Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
I think you misunderstood my proposed syntax. To clarify: enum Suit { let bezierPath: UIBezierPath // Stored property declaration case spades { let bezierPath = UIBezierPath() // Declare and initialize and local variable, this is not stored property declaration // add drawing commands to bezierPath self.bezierPath = bezierPath // Initialize stored property with local variable. Stored property is shared among cases } } I agree that cases should not be treated as pseudo-type, I am not proposing that. What I am proposing is the that enum instance behaviour and data can be very dependent of it case. And that there should be easier and clearer ways to configure that using stored properties. On Thu, Jun 2, 2016 at 10:26 AM, Brent Royal-Gordonwrote: >> As stated before it supposed to be per case initialization. You cannot >> really have this analogy with other types as they have type and >> instance while enums have type, case and instance. > > No. If structs have just type and instance, then so do enums. > > Cases in enums are analogous to stored properties in structs: they are a > means of organizing and representing concrete storage. They are not > first-class entities in the way that types and instances are. Much mischief > comes from thinking of cases as pseudo-types, or as some sort of peer to a > type. > >> But consider this: >> >> struct Struct { >>static let bezierPath: UIBezierPath // shared >> >>static func initialize() { >>bezierPath = UIBezierPath() >>} >> } > > Yes, because there's a `static` keyword on that declaration. That marks it as > something different from an ordinary `let`. Similarly, part of the idea of my > use of accessors is that the `accessor` keyword marks it as something > different from an ordinary `var`. > > (Also, you shouldn't use `initialize()` in Swift; you should set the variable > directly. Also also, I'm pretty sure that wouldn't work at all, because > `initialize()` is a normal method, not an initializer, and `bezierPath` is a > constant.) > > -- > Brent Royal-Gordon > Architechies > ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
> As stated before it supposed to be per case initialization. You cannot > really have this analogy with other types as they have type and > instance while enums have type, case and instance. No. If structs have just type and instance, then so do enums. Cases in enums are analogous to stored properties in structs: they are a means of organizing and representing concrete storage. They are not first-class entities in the way that types and instances are. Much mischief comes from thinking of cases as pseudo-types, or as some sort of peer to a type. > But consider this: > > struct Struct { >static let bezierPath: UIBezierPath // shared > >static func initialize() { >bezierPath = UIBezierPath() >} > } Yes, because there's a `static` keyword on that declaration. That marks it as something different from an ordinary `let`. Similarly, part of the idea of my use of accessors is that the `accessor` keyword marks it as something different from an ordinary `var`. (Also, you shouldn't use `initialize()` in Swift; you should set the variable directly. Also also, I'm pretty sure that wouldn't work at all, because `initialize()` is a normal method, not an initializer, and `bezierPath` is a constant.) -- Brent Royal-Gordon Architechies ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
As stated before it supposed to be per case initialization. You cannot really have this analogy with other types as they have type and instance while enums have type, case and instance. But consider this: struct Struct { static let bezierPath: UIBezierPath // shared static func initialize() { bezierPath = UIBezierPath() } } On Thu, Jun 2, 2016 at 12:18 AM, Brent Royal-Gordonwrote: >> UIBezierPath is shared for all instances of the enum case. So stored >> properties are stored per case, not per instance (you have associated >> values for per instance values). >> >>> that isn't really what this syntax suggests is happening >> >> Please explain what makes you think that way. > > Because you wrote `let bezierPath = UIBezierPath()` in the middle of a type > definition, and in all other types, you would get a new bezier path for each > instance. > > struct Struct { > let bezierPath = UIBezierPath() // per instance > } > class Class { > let bezierPath = UIBezierPath() // per instance > } > func function() { > let bezierPath = UIBezierPath() // per call > } > enum Enum { > case aCase { > let bezierPath = UIBezierPath() // shared?!?! > } > } > > -- > Brent Royal-Gordon > Architechies > ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
> UIBezierPath is shared for all instances of the enum case. So stored > properties are stored per case, not per instance (you have associated > values for per instance values). > >> that isn't really what this syntax suggests is happening > > Please explain what makes you think that way. Because you wrote `let bezierPath = UIBezierPath()` in the middle of a type definition, and in all other types, you would get a new bezier path for each instance. struct Struct { let bezierPath = UIBezierPath() // per instance } class Class { let bezierPath = UIBezierPath() // per instance } func function() { let bezierPath = UIBezierPath() // per call } enum Enum { case aCase { let bezierPath = UIBezierPath() // shared?!?! } } -- Brent Royal-Gordon Architechies ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
Hello David, Could you elaborate on this more? Seeing the possibilities of FSM's in Swift using its powerful enum and case pattern matching was one of the moments in which Swift started increasing its allure factor ;). Part 1 (background and theory): http://www.figure.ink/blog/2015/1/31/swift-state-machines-part-1 Part 2 (start of the implementation): http://www.figure.ink/blog/2015/2/1/swift-state-machines-part-2 Part 3: http://www.figure.ink/blog/2015/2/8/swift-state-machines-part-3-follow-up Part 4: http://www.figure.ink/blog/2015/2/9/swift-state-machines-part-4-redirect Final gist: https://gist.github.com/jemmons/f30f1de292751da0f1b7 On Wed, Jun 1, 2016 at 3:48 PM, David Waite via swift-evolution < swift-evolution@swift.org> wrote: > One thing I did often in Java (and miss in Swift) is using their enums to > build state machines or implement command patterns for common commands. > > Java enums are a sealed set of subclasses of the enum base type with > (hopefully) immutable, singleton instances. So you can do fun things like: > - Define the base class constructor to be called to instantiate the > subclasses, and declare the cases with the constructor arguments > - Declare a method on the base type and refine it on 1-2 particular cases > - Declare the enum implements an interface, and implement that interface > separately for each case. > - Define data accessors specific to the type (such as the planets example > above) > > I like the SuitInfo approach below - with extensions, I think I can get > close to what I have done in the past with Java. Maybe one day there is > syntax to do this in the language directly > > -DW > > > On May 31, 2016, at 11:44 AM, Vladimir.S via swift-evolution < > swift-evolution@swift.org> wrote: > > > > I'm not sure about my opinion on this proposal, but I believe you should > add this as alternatives of how we can have the similar features today > without injecting stored properties into enums : > > > > enum Suit { > >case spades > >case hearts > >case diamonds > >case clubs > > > >struct SuitInfo { > >let simpleDescription: String > >let color: UIColor > >let symbol: String > >let bezierPath: UIBezierPath > >} > > > >var info : SuitInfo { > >switch self { > >case .spades: > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "spades", > >color: .blackColor(), > >symbol: "♠", > >bezierPath: path) > > > >case .hearts: > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "hearts", > >color: .redColor(), > >symbol: "♥", > >bezierPath: path) > > > >case .diamonds: > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "diamonds", > >color: .redColor(), > >symbol: "♦", > >bezierPath: path) > > > >case .clubs: > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "clubs", > >color: .blackColor(), > >symbol: "♣", > >bezierPath: path) > > > >} > >} > > } > > > > and this: > > > > enum Suit { > >case spades > >case hearts > >case diamonds > >case clubs > > > >struct SuitInfo { > >let simpleDescription: String > >let color: UIColor > >let symbol: String > >let bezierPath: UIBezierPath > >} > > > >static let spadesInfo : SuitInfo = { > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "spades", > >color: .blackColor(), > >symbol: "♠", > >bezierPath: path) > >}() > > > >static let heartsInfo : SuitInfo = { > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "hearts", > >color: .redColor(), > >symbol: "♥", > >bezierPath: path) > >}() > > > >static let diamondsInfo : SuitInfo = { > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "diamonds", > >color: .redColor(), > >symbol: "♦", > >bezierPath: path) > >}() > > > >static let clubsInfo : SuitInfo = { > >let path = UIBezierPath() > >// omitted lines ... > > > >return SuitInfo( > >simpleDescription: "clubs", > >color: .blackColor(), > >symbol: "♣", > >
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
I'm not much fond of Java enums but then Java also doesn't have structs so I think enums there were created to be a mix of structs and enums and that's why you can do all the things you mention on your list. That said: - The tuple typed enum approach is the closest thing we discussed to constructors like the ones in Java enums; - I never knew one could do that in Java but I think tuples can hold function types; - I also never heard one can do that in Java but I begin to think what you really want are structs here; - Both approaches here provide that, but accessors would allow for dynamic content to be generated, not static. Also Swift already allow for functions to be declared in enums and I think this would be a better place than accessor properties to place code that will generate dynamic results. L On 1 June 2016 at 11:59, Matthew Johnson via swift-evolutionwrote: > > > Sent from my iPad > >> On Jun 1, 2016, at 9:48 AM, David Waite via swift-evolution >> wrote: >> >> One thing I did often in Java (and miss in Swift) is using their enums to >> build state machines or implement command patterns for common commands. >> >> Java enums are a sealed set of subclasses of the enum base type with >> (hopefully) immutable, singleton instances. So you can do fun things like: >> - Define the base class constructor to be called to instantiate the >> subclasses, and declare the cases with the constructor arguments >> - Declare a method on the base type and refine it on 1-2 particular cases >> - Declare the enum implements an interface, and implement that interface >> separately for each case. >> - Define data accessors specific to the type (such as the planets example >> above) >> >> I like the SuitInfo approach below - with extensions, I think I can get >> close to what I have done in the past with Java. Maybe one day there is >> syntax to do this in the language directly > > This is pretty similar to what we were discussing last week in this thread: > https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160523/018799.html > > I'm planning to write up a proposal when I have time (hopefully in the next > week or so). > >> >> -DW >> >>> On May 31, 2016, at 11:44 AM, Vladimir.S via swift-evolution >>> wrote: >>> >>> I'm not sure about my opinion on this proposal, but I believe you should >>> add this as alternatives of how we can have the similar features today >>> without injecting stored properties into enums : >>> >>> enum Suit { >>> case spades >>> case hearts >>> case diamonds >>> case clubs >>> >>> struct SuitInfo { >>> let simpleDescription: String >>> let color: UIColor >>> let symbol: String >>> let bezierPath: UIBezierPath >>> } >>> >>> var info : SuitInfo { >>> switch self { >>> case .spades: >>> let path = UIBezierPath() >>> // omitted lines ... >>> >>> return SuitInfo( >>> simpleDescription: "spades", >>> color: .blackColor(), >>> symbol: "♠", >>> bezierPath: path) >>> >>> case .hearts: >>> let path = UIBezierPath() >>> // omitted lines ... >>> >>> return SuitInfo( >>> simpleDescription: "hearts", >>> color: .redColor(), >>> symbol: "♥", >>> bezierPath: path) >>> >>> case .diamonds: >>> let path = UIBezierPath() >>> // omitted lines ... >>> >>> return SuitInfo( >>> simpleDescription: "diamonds", >>> color: .redColor(), >>> symbol: "♦", >>> bezierPath: path) >>> >>> case .clubs: >>> let path = UIBezierPath() >>> // omitted lines ... >>> >>> return SuitInfo( >>> simpleDescription: "clubs", >>> color: .blackColor(), >>> symbol: "♣", >>> bezierPath: path) >>> >>> } >>> } >>> } >>> >>> and this: >>> >>> enum Suit { >>> case spades >>> case hearts >>> case diamonds >>> case clubs >>> >>> struct SuitInfo { >>> let simpleDescription: String >>> let color: UIColor >>> let symbol: String >>> let bezierPath: UIBezierPath >>> } >>> >>> static let spadesInfo : SuitInfo = { >>> let path = UIBezierPath() >>> // omitted lines ... >>> >>> return SuitInfo( >>> simpleDescription: "spades", >>> color: .blackColor(), >>> symbol: "♠", >>> bezierPath: path) >>> }() >>> >>> static let heartsInfo : SuitInfo = { >>> let path = UIBezierPath() >>> // omitted lines ... >>> >>> return SuitInfo( >>> simpleDescription: "hearts", >>> color: .redColor(), >>> symbol: "♥", >>> bezierPath: path) >>> }() >>> >>> static let diamondsInfo : SuitInfo = { >>>
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
> On Jun 1, 2016, at 9:48 AM, David Waite via swift-evolution >wrote: > > One thing I did often in Java (and miss in Swift) is using their enums to > build state machines or implement command patterns for common commands. > > Java enums are a sealed set of subclasses of the enum base type with > (hopefully) immutable, singleton instances. So you can do fun things like: > - Define the base class constructor to be called to instantiate the > subclasses, and declare the cases with the constructor arguments > - Declare a method on the base type and refine it on 1-2 particular cases > - Declare the enum implements an interface, and implement that interface > separately for each case. > - Define data accessors specific to the type (such as the planets example > above) +1 to this behavior — one of the increasingly rare places where Java is nicer than Swift. This is the natural generalization / next step of the stored properties of this thread, and I can confirm what David said: it’s useful in practice. P ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
Sent from my iPad > On Jun 1, 2016, at 9:48 AM, David Waite via swift-evolution >wrote: > > One thing I did often in Java (and miss in Swift) is using their enums to > build state machines or implement command patterns for common commands. > > Java enums are a sealed set of subclasses of the enum base type with > (hopefully) immutable, singleton instances. So you can do fun things like: > - Define the base class constructor to be called to instantiate the > subclasses, and declare the cases with the constructor arguments > - Declare a method on the base type and refine it on 1-2 particular cases > - Declare the enum implements an interface, and implement that interface > separately for each case. > - Define data accessors specific to the type (such as the planets example > above) > > I like the SuitInfo approach below - with extensions, I think I can get close > to what I have done in the past with Java. Maybe one day there is syntax to > do this in the language directly This is pretty similar to what we were discussing last week in this thread: https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160523/018799.html I'm planning to write up a proposal when I have time (hopefully in the next week or so). > > -DW > >> On May 31, 2016, at 11:44 AM, Vladimir.S via swift-evolution >> wrote: >> >> I'm not sure about my opinion on this proposal, but I believe you should add >> this as alternatives of how we can have the similar features today without >> injecting stored properties into enums : >> >> enum Suit { >> case spades >> case hearts >> case diamonds >> case clubs >> >> struct SuitInfo { >> let simpleDescription: String >> let color: UIColor >> let symbol: String >> let bezierPath: UIBezierPath >> } >> >> var info : SuitInfo { >> switch self { >> case .spades: >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "spades", >> color: .blackColor(), >> symbol: "♠", >> bezierPath: path) >> >> case .hearts: >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "hearts", >> color: .redColor(), >> symbol: "♥", >> bezierPath: path) >> >> case .diamonds: >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "diamonds", >> color: .redColor(), >> symbol: "♦", >> bezierPath: path) >> >> case .clubs: >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "clubs", >> color: .blackColor(), >> symbol: "♣", >> bezierPath: path) >> >> } >> } >> } >> >> and this: >> >> enum Suit { >> case spades >> case hearts >> case diamonds >> case clubs >> >> struct SuitInfo { >> let simpleDescription: String >> let color: UIColor >> let symbol: String >> let bezierPath: UIBezierPath >> } >> >> static let spadesInfo : SuitInfo = { >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "spades", >> color: .blackColor(), >> symbol: "♠", >> bezierPath: path) >> }() >> >> static let heartsInfo : SuitInfo = { >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "hearts", >> color: .redColor(), >> symbol: "♥", >> bezierPath: path) >> }() >> >> static let diamondsInfo : SuitInfo = { >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "diamonds", >> color: .redColor(), >> symbol: "♦", >> bezierPath: path) >> }() >> >> static let clubsInfo : SuitInfo = { >> let path = UIBezierPath() >> // omitted lines ... >> >> return SuitInfo( >> simpleDescription: "clubs", >> color: .blackColor(), >> symbol: "♣", >> bezierPath: path) >> }() >> >> >> var info : SuitInfo { >> switch self { >> case .spades: return Suit.spadesInfo >> case .hearts: return Suit.heartsInfo >> case .diamonds: return Suit.diamondsInfo >> case .clubs: return Suit.clubsInfo >> } >> } >> } >> >> >>> On 31.05.2016 17:17, Jānis Kiršteins via swift-evolution wrote: >>> I wrote a proposal draft: >>> >>> # Enum case stored properties >>> >>> * Proposal: TBD >>> * Author: [Janis Kirsteins](https://github.com/kirsteins) >>>
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
One thing I did often in Java (and miss in Swift) is using their enums to build state machines or implement command patterns for common commands. Java enums are a sealed set of subclasses of the enum base type with (hopefully) immutable, singleton instances. So you can do fun things like: - Define the base class constructor to be called to instantiate the subclasses, and declare the cases with the constructor arguments - Declare a method on the base type and refine it on 1-2 particular cases - Declare the enum implements an interface, and implement that interface separately for each case. - Define data accessors specific to the type (such as the planets example above) I like the SuitInfo approach below - with extensions, I think I can get close to what I have done in the past with Java. Maybe one day there is syntax to do this in the language directly -DW > On May 31, 2016, at 11:44 AM, Vladimir.S via swift-evolution >wrote: > > I'm not sure about my opinion on this proposal, but I believe you should add > this as alternatives of how we can have the similar features today without > injecting stored properties into enums : > > enum Suit { >case spades >case hearts >case diamonds >case clubs > >struct SuitInfo { >let simpleDescription: String >let color: UIColor >let symbol: String >let bezierPath: UIBezierPath >} > >var info : SuitInfo { >switch self { >case .spades: >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "spades", >color: .blackColor(), >symbol: "♠", >bezierPath: path) > >case .hearts: >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "hearts", >color: .redColor(), >symbol: "♥", >bezierPath: path) > >case .diamonds: >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "diamonds", >color: .redColor(), >symbol: "♦", >bezierPath: path) > >case .clubs: >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "clubs", >color: .blackColor(), >symbol: "♣", >bezierPath: path) > >} >} > } > > and this: > > enum Suit { >case spades >case hearts >case diamonds >case clubs > >struct SuitInfo { >let simpleDescription: String >let color: UIColor >let symbol: String >let bezierPath: UIBezierPath >} > >static let spadesInfo : SuitInfo = { >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "spades", >color: .blackColor(), >symbol: "♠", >bezierPath: path) >}() > >static let heartsInfo : SuitInfo = { >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "hearts", >color: .redColor(), >symbol: "♥", >bezierPath: path) >}() > >static let diamondsInfo : SuitInfo = { >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "diamonds", >color: .redColor(), >symbol: "♦", >bezierPath: path) >}() > >static let clubsInfo : SuitInfo = { >let path = UIBezierPath() >// omitted lines ... > >return SuitInfo( >simpleDescription: "clubs", >color: .blackColor(), >symbol: "♣", >bezierPath: path) >}() > > >var info : SuitInfo { >switch self { >case .spades: return Suit.spadesInfo >case .hearts: return Suit.heartsInfo >case .diamonds: return Suit.diamondsInfo >case .clubs: return Suit.clubsInfo >} >} > } > > > On 31.05.2016 17:17, Jānis Kiršteins via swift-evolution wrote: >> I wrote a proposal draft: >> >> # Enum case stored properties >> >> * Proposal: TBD >> * Author: [Janis Kirsteins](https://github.com/kirsteins) >> * Status: TBD >> * Review manager: TBD >> >> ## Introduction >> >> This proposal allows each enum case to have stored properties. >> >> ## Motivation >> >> Enums cases can have a lot of constant (or variable) static values >> associated with it. For example, planets can have mass, radius, age, >> closest star etc. Currently there is no way to set or get those values >> easily. >> >> Example below shows that is hard to read and manage static associated
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
UIBezierPath is shared for all instances of the enum case. So stored properties are stored per case, not per instance (you have associated values for per instance values). > that isn't really what this syntax suggests is happening Please explain what makes you think that way. On Tue, May 31, 2016 at 11:52 PM, Brent Royal-Gordonwrote: >>case spades { > >>let bezierPath = UIBezierPath() > > Does each instance of `.spades` have a *separate* UIBezierPath, or do all > instances of `.spades` share one? If it's the former, I have strong doubts > you'll actually get this through. If it's the latter, that isn't really what > this syntax suggests is happening. > > -- > Brent Royal-Gordon > Architechies > ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
>case spades { >let bezierPath = UIBezierPath() Does each instance of `.spades` have a *separate* UIBezierPath, or do all instances of `.spades` share one? If it's the former, I have strong doubts you'll actually get this through. If it's the latter, that isn't really what this syntax suggests is happening. -- Brent Royal-Gordon Architechies ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
A huge +1 on the syntax change, which I think is a colossal improvement over the current situation and adds a lot of clarity to enum declarations. Neutral on the necessity to add actual stored properties to the enums. If the new syntax were merely syntactic sugar that would effectively generate the switch statements behind the scenes, that would work for me too, and would probably offend fewer people. Charles > On May 31, 2016, at 9:17 AM, Jānis Kiršteins via swift-evolution >wrote: > > I wrote a proposal draft: > > # Enum case stored properties > > * Proposal: TBD > * Author: [Janis Kirsteins](https://github.com/kirsteins) > * Status: TBD > * Review manager: TBD > > ## Introduction > > This proposal allows each enum case to have stored properties. > > ## Motivation > > Enums cases can have a lot of constant (or variable) static values > associated with it. For example, planets can have mass, radius, age, > closest star etc. Currently there is no way to set or get those values > easily. > > Example below shows that is hard to read and manage static associated > values with each case. It is hard to add or remove case as it would > require to add or remove code in four different places in file. Also > static associated value like `UIBezierPath` is recreated each time the > property is computed while it's constant. > > ```swift > enum Suit { >case spades >case hearts >case diamonds >case clubs > >var simpleDescription: String { >switch self { >case .spades: >return "spades" >case .hearts: >return "hearts" >case .diamonds: >return "diamonds" >case .clubs: >return "clubs" >} >} > >var color: UIColor { >switch self { >case .spades: >return .blackColor() >case .hearts: >return .redColor() >case .diamonds: >return .redColor() >case .clubs: >return .blackColor() >} >} > >var symbol: String { >switch self { >case .spades: >return "♠" >case .hearts: >return "♥" >case .diamonds: >return "♦" >case .clubs: >return "♣" >} >} > >var bezierPath: UIBezierPath { >switch self { >case .spades: >let path = UIBezierPath() >// omitted lines ... >return path >case .hearts: >let path = UIBezierPath() >// omitted lines ... >return path >case .diamonds: >let path = UIBezierPath() >// omitted lines ... >return path >case .clubs: >let path = UIBezierPath() >// omitted lines ... >return path >} >} > } > ``` > > ## Proposed solution > > Support stored properties for enum cases just as each case were an > instance. Case properties are initialized block after each case > declaration. > > ```swift > enum Suit { >let simpleDescription: String >let color: UIColor >let symbol: String >let bezierPath: UIBezierPath > >case spades { >simpleDescription = "spades" >color = .blackColor() >symbol = "♠" >let bezierPath = UIBezierPath() >// omitted lines ... >self.bezierPath = bezierPath >} > >case hearts { >simpleDescription = "hearts" >color = .redColor() >symbol = "♥" >let bezierPath = UIBezierPath() >// omitted lines ... >self.bezierPath = bezierPath >} > >case diamonds { >simpleDescription = "diamonds" >color = .redColor() >symbol = "♦" >let bezierPath = UIBezierPath() >// omitted lines ... >self.bezierPath = bezierPath >} > >case clubs { >simpleDescription = "clubs" >color = .blackColor() >symbol = "♣" >let bezierPath = UIBezierPath() >// omitted lines ... >self.bezierPath = bezierPath >} > } > > let symbol = Suit.spades.symbol // "♠" > ``` > > The proposed solution improves: > - Readability as cases are closer with their related data; > - Improves code maintainability as a case can be removed or added in one > place; > - Improved performance as there is no need to recreate static values; > - ~30% less lines of code in given example. > > ## Detailed design > > Stored properties > > Enum stored properties are supported the same way they are supported > for structs can classes. Unlike enum associated values, stored > properties are static to case and are shared for the same case. > > Properties are accessed: > ```swift > let simpleDescription = Suit.spades.simpleDescription > ``` > > Mutable properties can be set: > ```swift > Suit.spades.simpleDescription = "new simple description" > ``` > > Initialization > > If enum
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
I'm not sure about my opinion on this proposal, but I believe you should add this as alternatives of how we can have the similar features today without injecting stored properties into enums : enum Suit { case spades case hearts case diamonds case clubs struct SuitInfo { let simpleDescription: String let color: UIColor let symbol: String let bezierPath: UIBezierPath } var info : SuitInfo { switch self { case .spades: let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "spades", color: .blackColor(), symbol: "♠", bezierPath: path) case .hearts: let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "hearts", color: .redColor(), symbol: "♥", bezierPath: path) case .diamonds: let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "diamonds", color: .redColor(), symbol: "♦", bezierPath: path) case .clubs: let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "clubs", color: .blackColor(), symbol: "♣", bezierPath: path) } } } and this: enum Suit { case spades case hearts case diamonds case clubs struct SuitInfo { let simpleDescription: String let color: UIColor let symbol: String let bezierPath: UIBezierPath } static let spadesInfo : SuitInfo = { let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "spades", color: .blackColor(), symbol: "♠", bezierPath: path) }() static let heartsInfo : SuitInfo = { let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "hearts", color: .redColor(), symbol: "♥", bezierPath: path) }() static let diamondsInfo : SuitInfo = { let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "diamonds", color: .redColor(), symbol: "♦", bezierPath: path) }() static let clubsInfo : SuitInfo = { let path = UIBezierPath() // omitted lines ... return SuitInfo( simpleDescription: "clubs", color: .blackColor(), symbol: "♣", bezierPath: path) }() var info : SuitInfo { switch self { case .spades: return Suit.spadesInfo case .hearts: return Suit.heartsInfo case .diamonds: return Suit.diamondsInfo case .clubs: return Suit.clubsInfo } } } On 31.05.2016 17:17, Jānis Kiršteins via swift-evolution wrote: I wrote a proposal draft: # Enum case stored properties * Proposal: TBD * Author: [Janis Kirsteins](https://github.com/kirsteins) * Status: TBD * Review manager: TBD ## Introduction This proposal allows each enum case to have stored properties. ## Motivation Enums cases can have a lot of constant (or variable) static values associated with it. For example, planets can have mass, radius, age, closest star etc. Currently there is no way to set or get those values easily. Example below shows that is hard to read and manage static associated values with each case. It is hard to add or remove case as it would require to add or remove code in four different places in file. Also static associated value like `UIBezierPath` is recreated each time the property is computed while it's constant. ```swift enum Suit { case spades case hearts case diamonds case clubs var simpleDescription: String { switch self { case .spades: return "spades" case .hearts: return "hearts" case .diamonds: return "diamonds" case .clubs: return "clubs" } } var color: UIColor { switch self { case .spades: return .blackColor() case .hearts: return .redColor() case .diamonds: return .redColor() case .clubs: return .blackColor() } } var symbol: String { switch self { case .spades: return "♠" case .hearts: return "♥" case .diamonds: return "♦" case .clubs: return "♣" } } var bezierPath: UIBezierPath { switch self { case
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
I wrote a proposal draft: # Enum case stored properties * Proposal: TBD * Author: [Janis Kirsteins](https://github.com/kirsteins) * Status: TBD * Review manager: TBD ## Introduction This proposal allows each enum case to have stored properties. ## Motivation Enums cases can have a lot of constant (or variable) static values associated with it. For example, planets can have mass, radius, age, closest star etc. Currently there is no way to set or get those values easily. Example below shows that is hard to read and manage static associated values with each case. It is hard to add or remove case as it would require to add or remove code in four different places in file. Also static associated value like `UIBezierPath` is recreated each time the property is computed while it's constant. ```swift enum Suit { case spades case hearts case diamonds case clubs var simpleDescription: String { switch self { case .spades: return "spades" case .hearts: return "hearts" case .diamonds: return "diamonds" case .clubs: return "clubs" } } var color: UIColor { switch self { case .spades: return .blackColor() case .hearts: return .redColor() case .diamonds: return .redColor() case .clubs: return .blackColor() } } var symbol: String { switch self { case .spades: return "♠" case .hearts: return "♥" case .diamonds: return "♦" case .clubs: return "♣" } } var bezierPath: UIBezierPath { switch self { case .spades: let path = UIBezierPath() // omitted lines ... return path case .hearts: let path = UIBezierPath() // omitted lines ... return path case .diamonds: let path = UIBezierPath() // omitted lines ... return path case .clubs: let path = UIBezierPath() // omitted lines ... return path } } } ``` ## Proposed solution Support stored properties for enum cases just as each case were an instance. Case properties are initialized block after each case declaration. ```swift enum Suit { let simpleDescription: String let color: UIColor let symbol: String let bezierPath: UIBezierPath case spades { simpleDescription = "spades" color = .blackColor() symbol = "♠" let bezierPath = UIBezierPath() // omitted lines ... self.bezierPath = bezierPath } case hearts { simpleDescription = "hearts" color = .redColor() symbol = "♥" let bezierPath = UIBezierPath() // omitted lines ... self.bezierPath = bezierPath } case diamonds { simpleDescription = "diamonds" color = .redColor() symbol = "♦" let bezierPath = UIBezierPath() // omitted lines ... self.bezierPath = bezierPath } case clubs { simpleDescription = "clubs" color = .blackColor() symbol = "♣" let bezierPath = UIBezierPath() // omitted lines ... self.bezierPath = bezierPath } } let symbol = Suit.spades.symbol // "♠" ``` The proposed solution improves: - Readability as cases are closer with their related data; - Improves code maintainability as a case can be removed or added in one place; - Improved performance as there is no need to recreate static values; - ~30% less lines of code in given example. ## Detailed design Stored properties Enum stored properties are supported the same way they are supported for structs can classes. Unlike enum associated values, stored properties are static to case and are shared for the same case. Properties are accessed: ```swift let simpleDescription = Suit.spades.simpleDescription ``` Mutable properties can be set: ```swift Suit.spades.simpleDescription = "new simple description" ``` Initialization If enum has uninitialized stored property it must be initialized in a block after each case declaration. The block work the same way as struct initialization. At the end of initialization block all properties must be initialized. ```swift enum Suit { var simpleDescription: String case spades { simpleDescription = "spades" } } ``` Initialization block can be combine with use of `rawValue`: ```swift enum Suit: Int { var simpleDescription: String case spades = 1 { simpleDescription = "spades" } } ``` or associated values of the case: ```swift enum Suit { var simpleDescription: String case spades(Int) { simpleDescription = "spades" } } ``` ## Impact on existing code Stored properties for enums are not currently not
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
I think that's the case with enums. You're changing their current behaviour of only having stored values to one in which it's computed (even if only once and then stored). Enums are IMO something that have a static value you know beforehand and can count on. That's why I'm not fond of the accessor proposal. Otherwise I think we're transforming enums into a closed set of struct instances and one could do that already by using a private init. > On 29 May 2016, at 3:38 am, Jānis Kiršteins via swift-evolution >wrote: > > I agree with the argument about use of "where", not replacing the raw > value and having some kind of initialization block. But I cannot see > why "accessors" concept is any better than stored properties to solve > the particular problem. The "accessors" concept has much wider scope > than enums and is a separate proposal. > > On Sat, May 28, 2016 at 11:39 PM, Brent Royal-Gordon > wrote: - Abusing rawValue is just that: an abuse. >>> >>> My original proposal does not replace rawValue and is compatible with it. >> >> `rawValue` has a different purpose from how you're using it. It's supposed >> to allow you to convert your type to some other *equivalent* type, like an >> equivalent integer or string. Moreover, it's supposed to allow you to >> *reconstruct* the instance from the raw value—remember, `RawRepresentable` >> has an `init(rawValue:)` requirement. >> >> It is *not* supposed to be an ancillary bag of information on the side. >> You're cramming a square peg into a round hole here. >> >> (Also, if you use `rawValue` for an ancillary bag of information, that means >> you *can't* use it on the same type for its intended purpose. For instance, >> you would not be able to assign numbers to your Planet enum's cases to help >> you serialize them or bridge them to Objective-C. That's not good.) >> - Using `where` just doesn't match the use of `where` elsewhere in the language; everywhere else, it's some kind of condition. >>> >>> It is also used in generic type constraints. Plus it reads like human >>> language: `case mercury where (mass: 3.303e+23, radius: 2.4397e6)` >> >> But a generic constraint is also a type of condition: it specifies types >> which are permitted and divides them from types that are not. >> >> This is *not* a condition. It's not anything like a condition. It's simply >> not consistent with anything else in the language. >> - Dictionaries are the most straightforward way to handle this with the current language, but their lack of exhaustiveness checking is a problem. >>> >>> Dictionaries can be used as workaround, but they cannot (lack of >>> exhaustiveness) solve the problem. >> >> I agree that they're a halfway solution. >> >> If `ValuesEnumerable` were to be accepted (and to have a generic requirement >> for its `allValues` property), you could write a Dictionary-like type which >> ensured at initialization time that it was exhaustive. That's not as good as >> compile time, but it's not bad—sort of a three-quarters solution. >> >>struct ExhaustiveDictionary> ValuesEnumerable>: Collection, DictionaryLiteralConvertible { >>private var dictionary: [Key: Value] >> >>init(dictionaryLiteral elements: (Key, Value)...) { >>dictionary = [:] >>for (k, v) in elements { >>dictionary[k] = v >>} >> >>if dictionary.count != Key.allValues.count { >>let missingKeys = Key.allValues.filter { >> dictionary[$0] == nil } >>preconditionFailure("ExhaustiveDictionary is >> missing elements from \(Key.self): \(missingKeys)") >>} >>} >> >>var startIndex: Dictionary.Index { >>return dictionary.startIndex >>} >>var endIndex: Dictionary.Index { >>return dictionary.endIndex >>} >>subscript(index: Dictionary.Index) -> (Key, Value) { >>return dictionary[index] >>} >>func index(after i: Dictionary.Index) -> Dictionary.Index { >>return dictionary.index(after: i) >>} >> >>subscript(key: Key) -> Value { >>get { return dictionary[key]! } >>set { dictionary[key] = newValue } >>} >>} >> What I would do is borrow the "accessors" concept from the property behaviors proposal and extend it so that it supported both functions and variables. >>> >>> Wouldn't accessor just be a redundant keyword here? Currently enums do >>> not support stored properties, so I guess there is no extra need to >>> mark
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
I agree with the argument about use of "where", not replacing the raw value and having some kind of initialization block. But I cannot see why "accessors" concept is any better than stored properties to solve the particular problem. The "accessors" concept has much wider scope than enums and is a separate proposal. On Sat, May 28, 2016 at 11:39 PM, Brent Royal-Gordonwrote: >>> - Abusing rawValue is just that: an abuse. >> >> My original proposal does not replace rawValue and is compatible with it. > > `rawValue` has a different purpose from how you're using it. It's supposed to > allow you to convert your type to some other *equivalent* type, like an > equivalent integer or string. Moreover, it's supposed to allow you to > *reconstruct* the instance from the raw value—remember, `RawRepresentable` > has an `init(rawValue:)` requirement. > > It is *not* supposed to be an ancillary bag of information on the side. > You're cramming a square peg into a round hole here. > > (Also, if you use `rawValue` for an ancillary bag of information, that means > you *can't* use it on the same type for its intended purpose. For instance, > you would not be able to assign numbers to your Planet enum's cases to help > you serialize them or bridge them to Objective-C. That's not good.) > >>> - Using `where` just doesn't match the use of `where` elsewhere in the >>> language; everywhere else, it's some kind of condition. >> >> It is also used in generic type constraints. Plus it reads like human >> language: `case mercury where (mass: 3.303e+23, radius: 2.4397e6)` > > But a generic constraint is also a type of condition: it specifies types > which are permitted and divides them from types that are not. > > This is *not* a condition. It's not anything like a condition. It's simply > not consistent with anything else in the language. > >>> - Dictionaries are the most straightforward way to handle this with the >>> current language, but their lack of exhaustiveness checking is a problem. >> >> Dictionaries can be used as workaround, but they cannot (lack of >> exhaustiveness) solve the problem. > > I agree that they're a halfway solution. > > If `ValuesEnumerable` were to be accepted (and to have a generic requirement > for its `allValues` property), you could write a Dictionary-like type which > ensured at initialization time that it was exhaustive. That's not as good as > compile time, but it's not bad—sort of a three-quarters solution. > > struct ExhaustiveDictionary ValuesEnumerable>: Collection, DictionaryLiteralConvertible { > private var dictionary: [Key: Value] > > init(dictionaryLiteral elements: (Key, Value)...) { > dictionary = [:] > for (k, v) in elements { > dictionary[k] = v > } > > if dictionary.count != Key.allValues.count { > let missingKeys = Key.allValues.filter { > dictionary[$0] == nil } > preconditionFailure("ExhaustiveDictionary is > missing elements from \(Key.self): \(missingKeys)") > } > } > > var startIndex: Dictionary.Index { > return dictionary.startIndex > } > var endIndex: Dictionary.Index { > return dictionary.endIndex > } > subscript(index: Dictionary.Index) -> (Key, Value) { > return dictionary[index] > } > func index(after i: Dictionary.Index) -> Dictionary.Index { > return dictionary.index(after: i) > } > > subscript(key: Key) -> Value { > get { return dictionary[key]! } > set { dictionary[key] = newValue } > } > } > >>> What I would do is borrow the "accessors" concept from the property >>> behaviors proposal and extend it so that it supported both functions and >>> variables. >> >> Wouldn't accessor just be a redundant keyword here? Currently enums do >> not support stored properties, so I guess there is no extra need to >> mark properties with any special keyword. > > The keyword is mainly to indicate the unusual syntax at the definition site, > where you only have to specify the name of the accessor you're defining, not > a `func` or `var` keyword, a return type, or even parameter names. (Like > `willSet`, there's a default parameter name you can use.) Secondarily, > though, I think it's helpful to indicate very explicitly that this is not an > ordinary method or property definition, even if the compiler could perhaps > sort things out without it. `accessor` is something a user can Google if > they've never seen it before. > >> Property accessors might work for
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
>> - Abusing rawValue is just that: an abuse. > > My original proposal does not replace rawValue and is compatible with it. `rawValue` has a different purpose from how you're using it. It's supposed to allow you to convert your type to some other *equivalent* type, like an equivalent integer or string. Moreover, it's supposed to allow you to *reconstruct* the instance from the raw value—remember, `RawRepresentable` has an `init(rawValue:)` requirement. It is *not* supposed to be an ancillary bag of information on the side. You're cramming a square peg into a round hole here. (Also, if you use `rawValue` for an ancillary bag of information, that means you *can't* use it on the same type for its intended purpose. For instance, you would not be able to assign numbers to your Planet enum's cases to help you serialize them or bridge them to Objective-C. That's not good.) >> - Using `where` just doesn't match the use of `where` elsewhere in the >> language; everywhere else, it's some kind of condition. > > It is also used in generic type constraints. Plus it reads like human > language: `case mercury where (mass: 3.303e+23, radius: 2.4397e6)` But a generic constraint is also a type of condition: it specifies types which are permitted and divides them from types that are not. This is *not* a condition. It's not anything like a condition. It's simply not consistent with anything else in the language. >> - Dictionaries are the most straightforward way to handle this with the >> current language, but their lack of exhaustiveness checking is a problem. > > Dictionaries can be used as workaround, but they cannot (lack of > exhaustiveness) solve the problem. I agree that they're a halfway solution. If `ValuesEnumerable` were to be accepted (and to have a generic requirement for its `allValues` property), you could write a Dictionary-like type which ensured at initialization time that it was exhaustive. That's not as good as compile time, but it's not bad—sort of a three-quarters solution. struct ExhaustiveDictionary: Collection, DictionaryLiteralConvertible { private var dictionary: [Key: Value] init(dictionaryLiteral elements: (Key, Value)...) { dictionary = [:] for (k, v) in elements { dictionary[k] = v } if dictionary.count != Key.allValues.count { let missingKeys = Key.allValues.filter { dictionary[$0] == nil } preconditionFailure("ExhaustiveDictionary is missing elements from \(Key.self): \(missingKeys)") } } var startIndex: Dictionary.Index { return dictionary.startIndex } var endIndex: Dictionary.Index { return dictionary.endIndex } subscript(index: Dictionary.Index) -> (Key, Value) { return dictionary[index] } func index(after i: Dictionary.Index) -> Dictionary.Index { return dictionary.index(after: i) } subscript(key: Key) -> Value { get { return dictionary[key]! } set { dictionary[key] = newValue } } } >> What I would do is borrow the "accessors" concept from the property >> behaviors proposal and extend it so that it supported both functions and >> variables. > > Wouldn't accessor just be a redundant keyword here? Currently enums do > not support stored properties, so I guess there is no extra need to > mark properties with any special keyword. The keyword is mainly to indicate the unusual syntax at the definition site, where you only have to specify the name of the accessor you're defining, not a `func` or `var` keyword, a return type, or even parameter names. (Like `willSet`, there's a default parameter name you can use.) Secondarily, though, I think it's helpful to indicate very explicitly that this is not an ordinary method or property definition, even if the compiler could perhaps sort things out without it. `accessor` is something a user can Google if they've never seen it before. > Property accessors might work for enums with associated values, but > not so well without them. The two have nothing to do with each other. I showed your planets example, which has no associated values but uses accessors just fine. -- Brent Royal-Gordon Architechies ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
> The suggested solution based on 'accessor' - will create assotiated > properties each time the enum instace created, for each instance of enum type. No; property accessors would be either computed or constant (so that all instances of a given case can share storage). This is much the way they would behave if they were included in behaviors. You could write a property accessor with a setter, but it would have to be computed, and manipulate `self`'s cases and associated values: enum Optional { accessor var unwrapped: T { get set } case none { unwrapped { get { fatalError("No value") } set { self = .some(newValue) } } } case some (_ value: T) { unwrapped { get { return value } set { self = .some(newValue) } } } } -- Brent Royal-Gordon Architechies ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
Correct me if I'm wrong, but this idea with accessors is not the same as static properties for each case. The one of ideas of initial proposal - static(!) values would be created only once and it is important in case it is expensive to create such value(or if should be created only once per case) The suggested solution based on 'accessor' - will create assotiated properties each time the enum instace created, for each instance of enum type. We can have something like the example with accessors now : enum MyError: ErrorProtocol { struct MyErrorInfo { let localizedFailureReason: String let url: String } case fileNotFound(url: String) case fileIsCorrupt(url: String) var info : MyErrorInfo { switch self { case fileNotFound(let url) : return MyErrorInfo(localizedFailureReason: "File \"\(url.lowercased())\" not found.", url: url) case fileIsCorrupt(let url) : return MyErrorInfo(localizedFailureReason: "File \"\(url.lowercased())\" is corrupt.", url: url) } } } var e = MyError.fileNotFound(url: "http://something.some;) var info = e.info print(info.localizedFailureReason, info.url) But yes, such MyErrorInfo will be created on each `info.` call. This is worse that create MyErrorInfo once per each enum instance initialization, but IMO these solutions are close enough. In any case, I don't see why tuple for enum and enum with `accessor` can not co-exists. On 27.05.2016 2:28, Charles Srstka via swift-evolution wrote: On May 26, 2016, at 4:47 PM, Brent Royal-Gordon via swift-evolution> wrote: - Abusing rawValue is just that: an abuse. In addition, enums with associated types can’t have rawValues. Why is this relevant, you may ask? Because error enums are a huge use case for something like this. Being able to do the below would be great: enum MyError: ErrorProtocol { accessor var localizedFailureReason: String accessor var url: NSURL case FileNotFound(url: NSURL) { self.localizedFailureReason = “File \"\(url.lastPathComponent ?? “”)\” not found.” self.url = url } case FileIsCorrupt(url: NSURL) { self.localizedFailureReason = “File \"\(url.lastPathComponent ?? “”)\” is corrupt.” self.url = url } } This would be much cleaner than the existing method of using a switch to create a userInfo dictionary for creating an NSError to send to -[NSApplication presentError:] and similar methods. Charles ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
> On May 26, 2016, at 4:47 PM, Brent Royal-Gordon via swift-evolution >wrote: > > - Abusing rawValue is just that: an abuse. In addition, enums with associated types can’t have rawValues. Why is this relevant, you may ask? Because error enums are a huge use case for something like this. Being able to do the below would be great: enum MyError: ErrorProtocol { accessor var localizedFailureReason: String accessor var url: NSURL case FileNotFound(url: NSURL) { self.localizedFailureReason = “File \"\(url.lastPathComponent ?? “”)\” not found.” self.url = url } case FileIsCorrupt(url: NSURL) { self.localizedFailureReason = “File \"\(url.lastPathComponent ?? “”)\” is corrupt.” self.url = url } } This would be much cleaner than the existing method of using a switch to create a userInfo dictionary for creating an NSError to send to -[NSApplication presentError:] and similar methods. Charles ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
Re: [swift-evolution] [Proposal] Enums with static stored properties for each case
> On May 26, 2016, at 4:47 PM, Brent Royal-Gordon via swift-evolution >wrote: > >> The proposed solution is to have single static initializer for each >> enum case that initializes stored properties. For example, > > My opinions so far: > > - Abusing rawValue is just that: an abuse. > > - Using `where` just doesn't match the use of `where` elsewhere in the > language; everywhere else, it's some kind of condition. > > - Dictionaries are the most straightforward way to handle this with the > current language, but their lack of exhaustiveness checking is a problem. > > What I would do is borrow the "accessors" concept from the property behaviors > proposal and extend it so that it supported both functions and variables. > Then I would let you write this: > > enum Planet { > accessor var mass: Float > accessor var radius: Float > > case mercury { > mass = 3.303e+23 > radius = 2.4397e6 > } > case venus { > mass = 4.869e+24 > radius = 6.0518e6 > } > case earth { > mass = 5.976e+24 > radius = 6.37814e6 > } > case mars { > mass = 6.421e+23 > radius = 3.3972e6 > } > case jupiter { > mass = 1.9e+27 > radius = 7.1492e7 > } > case saturn { > mass = 5.688e+26 > radius = 6.0268e7 > } > case uranus { > mass = 8.686e+25 > radius = 2.5559e7 > } > case neptune { > mass = 1.024e+26 > radius = 2.4746e7 > } > } > > You would also be able to declare methods like this; each implementation > would just look like `methodName { code }`. And you could provide default > implementations too: > > enum Planet { > accessor var mass: Float > accessor var radius: Float > accessor var habitable: Bool = false > > case mercury { > mass = 3.303e+23 > radius = 2.4397e6 > } > case venus { > mass = 4.869e+24 > radius = 6.0518e6 > } > case earth { > mass = 5.976e+24 > radius = 6.37814e6 > habitable = true > } > case mars { > mass = 6.421e+23 > radius = 3.3972e6 > } > case jupiter { > mass = 1.9e+27 > radius = 7.1492e7 > } > case saturn { > mass = 5.688e+26 > radius = 6.0268e7 > } > case uranus { > mass = 8.686e+25 > radius = 2.5559e7 > } > case neptune { > mass = 1.024e+26 > radius = 2.4746e7 > } > } > This is the first really interesting (to me) idea in the thread. I think I like it but need to give it more thought to decide for sure. One really interesting thing we could do to build on this would be to introduce the associated value names inside the scope of each case as if they were member variables: enum Foo { accessor func bar() -> Int case baz(val: Int) { // val is in scope here func bar() { return val } } } > -- > Brent Royal-Gordon > Architechies > > ___ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
[swift-evolution] [Proposal] Enums with static stored properties for each case
Hello everyone, Currently Swift only supports computed properties for each enum case. If you want to somehow get static values with each case you would probably do it like this: enum Planet { case mercury case venus case earth case mars case jupiter case saturn case uranus case neptune var mass: Float { switch self { case .mercury: return 3.303e+23 case .venus: return 4.869e+24 case .earth: return 5.976e+24 case .mars: return 6.421e+23 case .jupiter: return 1.9e+27 case .saturn: return 5.688e+26 case .uranus: return 8.686e+25 case .neptune: return 1.024e+26 } } var radius: Float { switch self { case .mercury: return 2.4397e6 case .venus: return 6.0518e6 case .earth: return 6.37814e6 case .mars: return 3.3972e6 case .jupiter: return 7.1492e7 case .saturn: return 6.0268e7 case .uranus: return 2.5559e7 case .neptune: return 2.4746e7 } } } However I see two problems with this approach: 1. These value definitions are spread out and difficult to read and maintain (especially if you have many computed properties for each enum case); 2. These values are not static. They are computed each time property is accessed. This can be a problem when value is expensive to create. The proposed solution is to have single static initializer for each enum case that initializes stored properties. For example, enum Planet { var mass: Float var radius: Float static init(mass: Float, radius: Float) { self.mass = mass self.radius = radius } case mercury where (mass: 3.303e+23, radius: 2.4397e6) case venus where (mass: 4.869e+24, radius: 6.0518e6) case earth where (mass: 5.976e+24, radius: 6.37814e6) case mars where (mass: 6.421e+23, radius: 3.3972e6) case jupiter where (mass: 1.9e+27, radius: 7.1492e7) case saturn where (mass: 5.688e+26, radius: 6.0268e7) case uranus where (mass: 8.686e+25, radius: 2.5559e7) case neptune where (mass: 1.024e+26, radius: 2.4746e7) } This approach do not affect enums that have raw or associated values, or custom enum initializers: case A = "A" where (id: 0) or case B(Int, Int, Int) where (id: 0) Benefits: 1. Less verbosity 2. Improved readability 3. Related values are closer to each other 4. Static values are not recomputed ___ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution