Re: [swift-evolution] Optionals and nil in Switch statement

[David Hart via swift-evolution]

Perhaps it should provide a Fix-It, but I don't see it as an an issue, more as 
an opportunity to understand the pattern matching behind it :)

> On 29 Jun 2016, at 08:59, Charlie Monroe  wrote:
> 
> Yes, you get a warning. But I don't see why it should - when you're matching 
> against an optional, it's evident that you mean .some("Hello")... This should 
> be automatically inferred.
> 
> I find this a confusing part of the switch statement where 
> 
> let obj: Any? = "Hello"
> 
> switch obj {
> case let str as String:
> print("Hey, found String!")
> default:
> print("No find.")
> }
> 
> will print "Hey found String", but it won't allow you to match against a 
> string literal. This is one of the first things that I found confusing when I 
> first learned Swift.
> 
>> On Jun 29, 2016, at 8:49 AM, David Hart  wrote:
>> 
>> I don't see it as a bug. The if statement calls an equality function which 
>> promotes the lhs to an Optional (or that accepts a non optional as lhs - 
>> can't remember) but the switch statement does pattern matching. Does the the 
>> compiler warn you when pattern matching an optional with a non-optional case?
>> 
>>> On 29 Jun 2016, at 07:16, Charlie Monroe via swift-evolution 
>>>  wrote:
>>> 
>>> I nevertheless think that this is a bug and should be addressed. There is 
>>> no reason where
>>> 
>>> if stringOptional == stringNonOptional { ... }
>>> 
>>> works, but pretty much the same construct doesn't work in the switch-case. 
>>> It should be perhaps solved via a bugreport at http://bugs.swift.org and 
>>> via evolution, though...
>>> 
 On Jun 29, 2016, at 12:31 AM, Nevin Brackett-Rozinsky via swift-evolution 
  wrote:
 
 I just got home and tested. The answer is yes, `case "text"?` does work.
 
 let optStr : String? = "text"
 switch optStr {
 case nil : print("Nil")
 case "text"? : print("Success")
 default  : print("Default")
 }
 // Prints `Success`
 
 
 Nevin
 
> On Tue, Jun 28, 2016 at 12:27 PM, Nevin Brackett-Rozinsky 
>  wrote:
> Does `case "text"?` work?
> 
> 
>> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
>>  wrote:
>> Case .none:
>> Case .some("string"):
>> 
>> 
>>> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>>>  wrote:
>>> 
>>> Forgive me if this was/is discussed already, I am new to the process 
>>> here
>>> 
>>> (code is attached as a playground too)
>>> 
>>> 
>>> 
>>> Sometimes when I am working with a String? nil can be a reasonable 
>>> value, and what I want to do is something like the following:
>>> 
>>> import UIKit
>>> 
>>> 
>>> 
>>> var str:String? = "Hello, playground"
>>> 
>>> 
>>> 
>>> switch str{
>>> 
>>> case nil:
>>> 
>>> print("Nil!")
>>> 
>>> case "Hello, playground":  //it would be super nice if this worked.
>>> 
>>> print("Match")
>>> 
>>> default:
>>> 
>>> print("Some other non nil value?")
>>> 
>>> }
>>> 
>>> 
>>> 
>>> But it does not work, the orange  text is a compile time error, 
>>> "Expression pattern of type 'String' cannot match value of type 
>>> 'String?'. I realize that this can be replaced with a let statement 
>>> (case let s where s == "Hello, playground":), but that is verbose. 
>>> 
>>> Seems like the compiler could be OK with the orange text, since it is 
>>> clearly not nil.
>>> 
>>> Thoughts?
>>> 
>>> -Lucas
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> ___
>>> swift-evolution mailing list
>>> swift-evolution@swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
 
 ___
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 https://lists.swift.org/mailman/listinfo/swift-evolution
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Re: [swift-evolution] Optionals and nil in Switch statement

[Charlie Monroe via swift-evolution]

Yes, you get a warning. But I don't see why it should - when you're matching 
against an optional, it's evident that you mean .some("Hello")... This should 
be automatically inferred.

I find this a confusing part of the switch statement where 

let obj: Any? = "Hello"

switch obj {
case let str as String:
print("Hey, found String!")
default:
print("No find.")
}

will print "Hey found String", but it won't allow you to match against a string 
literal. This is one of the first things that I found confusing when I first 
learned Swift.

> On Jun 29, 2016, at 8:49 AM, David Hart  wrote:
> 
> I don't see it as a bug. The if statement calls an equality function which 
> promotes the lhs to an Optional (or that accepts a non optional as lhs - 
> can't remember) but the switch statement does pattern matching. Does the the 
> compiler warn you when pattern matching an optional with a non-optional case?
> 
> On 29 Jun 2016, at 07:16, Charlie Monroe via swift-evolution 
> > wrote:
> 
>> I nevertheless think that this is a bug and should be addressed. There is no 
>> reason where
>> 
>> if stringOptional == stringNonOptional { ... }
>> 
>> works, but pretty much the same construct doesn't work in the switch-case. 
>> It should be perhaps solved via a bugreport at http://bugs.swift.org 
>>  and via evolution, though...
>> 
>>> On Jun 29, 2016, at 12:31 AM, Nevin Brackett-Rozinsky via swift-evolution 
>>> > wrote:
>>> 
>>> I just got home and tested. The answer is yes, `case "text"?` does work.
>>> 
>>> let optStr : String? = "text"
>>> switch optStr {
>>> case nil : print("Nil")
>>> case "text"? : print("Success")
>>> default  : print("Default")
>>> }
>>> // Prints `Success`
>>> 
>>> 
>>> Nevin
>>> 
>>> On Tue, Jun 28, 2016 at 12:27 PM, Nevin Brackett-Rozinsky 
>>> >> > wrote:
>>> Does `case "text"?` work?
>>> 
>>> 
>>> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
>>> > wrote:
>>> Case .none:
>>> Case .some("string"):
>>> 
>>> 
>>> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>>> > wrote:
>>> 
 Forgive me if this was/is discussed already, I am new to the process 
 here
 
 (code is attached as a playground too)
 
 
 
 Sometimes when I am working with a String? nil can be a reasonable value, 
 and what I want to do is something like the following:
 
 import UIKit
 
 
 
 var str:String? = "Hello, playground"
 
 
 
 switch str{
 
 case nil:
 
 print("Nil!")
 
 case "Hello, playground":  //it would be super nice if this worked.
 
 print("Match")
 
 default:
 
 print("Some other non nil value?")
 
 }
 
 
 
 But it does not work, the orange  text is a compile time error, 
 "Expression pattern of type 'String' cannot match value of type 'String?'. 
 I realize that this can be replaced with a let statement (case let s where 
 s == "Hello, playground":), but that is verbose. 
 
 Seems like the compiler could be OK with the orange text, since it is 
 clearly not nil.
 
 Thoughts?
 
 -Lucas
 
 
 
 
 
 
 ___
 swift-evolution mailing list
 swift-evolution@swift.org <>
 https://lists.swift.org/mailman/listinfo/swift-evolution 
 
>>> 
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>>> https://lists.swift.org/mailman/listinfo/swift-evolution 
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>> 
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Re: [swift-evolution] Optionals and nil in Switch statement

[David Hart via swift-evolution]

I don't see it as a bug. The if statement calls an equality function which 
promotes the lhs to an Optional (or that accepts a non optional as lhs - can't 
remember) but the switch statement does pattern matching. Does the the compiler 
warn you when pattern matching an optional with a non-optional case?

> On 29 Jun 2016, at 07:16, Charlie Monroe via swift-evolution 
>  wrote:
> 
> I nevertheless think that this is a bug and should be addressed. There is no 
> reason where
> 
> if stringOptional == stringNonOptional { ... }
> 
> works, but pretty much the same construct doesn't work in the switch-case. It 
> should be perhaps solved via a bugreport at http://bugs.swift.org and via 
> evolution, though...
> 
>> On Jun 29, 2016, at 12:31 AM, Nevin Brackett-Rozinsky via swift-evolution 
>>  wrote:
>> 
>> I just got home and tested. The answer is yes, `case "text"?` does work.
>> 
>> let optStr : String? = "text"
>> switch optStr {
>> case nil : print("Nil")
>> case "text"? : print("Success")
>> default  : print("Default")
>> }
>> // Prints `Success`
>> 
>> 
>> Nevin
>> 
>>> On Tue, Jun 28, 2016 at 12:27 PM, Nevin Brackett-Rozinsky 
>>>  wrote:
>>> Does `case "text"?` work?
>>> 
>>> 
 On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
  wrote:
 Case .none:
 Case .some("string"):
 
 
> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>  wrote:
> 
> Forgive me if this was/is discussed already, I am new to the process 
> here
> 
> (code is attached as a playground too)
> 
> 
> 
> Sometimes when I am working with a String? nil can be a reasonable value, 
> and what I want to do is something like the following:
> 
> import UIKit
> 
> 
> 
> var str:String? = "Hello, playground"
> 
> 
> 
> switch str{
> 
> case nil:
> 
> print("Nil!")
> 
> case "Hello, playground":  //it would be super nice if this worked.
> 
> print("Match")
> 
> default:
> 
> print("Some other non nil value?")
> 
> }
> 
> 
> 
> But it does not work, the orange  text is a compile time error, 
> "Expression pattern of type 'String' cannot match value of type 
> 'String?'. I realize that this can be replaced with a let statement (case 
> let s where s == "Hello, playground":), but that is verbose. 
> 
> Seems like the compiler could be OK with the orange text, since it is 
> clearly not nil.
> 
> Thoughts?
> 
> -Lucas
> 
> 
> 
> 
> 
> 
> ___
> swift-evolution mailing list
> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>> 
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>> https://lists.swift.org/mailman/listinfo/swift-evolution
> 
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Re: [swift-evolution] Optionals and nil in Switch statement

[Charlie Monroe via swift-evolution]

I nevertheless think that this is a bug and should be addressed. There is no 
reason where

if stringOptional == stringNonOptional { ... }

works, but pretty much the same construct doesn't work in the switch-case. It 
should be perhaps solved via a bugreport at http://bugs.swift.org 
 and via evolution, though...

> On Jun 29, 2016, at 12:31 AM, Nevin Brackett-Rozinsky via swift-evolution 
>  wrote:
> 
> I just got home and tested. The answer is yes, `case "text"?` does work.
> 
> let optStr : String? = "text"
> switch optStr {
> case nil : print("Nil")
> case "text"? : print("Success")
> default  : print("Default")
> }
> // Prints `Success`
> 
> 
> Nevin
> 
> On Tue, Jun 28, 2016 at 12:27 PM, Nevin Brackett-Rozinsky 
> > 
> wrote:
> Does `case "text"?` work?
> 
> 
> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
> > wrote:
> Case .none:
> Case .some("string"):
> 
> 
> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
> > wrote:
> 
>> Forgive me if this was/is discussed already, I am new to the process here
>> 
>> (code is attached as a playground too)
>> 
>> 
>> 
>> Sometimes when I am working with a String? nil can be a reasonable value, 
>> and what I want to do is something like the following:
>> 
>> import UIKit
>> 
>> 
>> 
>> var str:String? = "Hello, playground"
>> 
>> 
>> 
>> switch str{
>> 
>> case nil:
>> 
>> print("Nil!")
>> 
>> case "Hello, playground":  //it would be super nice if this worked.
>> 
>> print("Match")
>> 
>> default:
>> 
>> print("Some other non nil value?")
>> 
>> }
>> 
>> 
>> 
>> But it does not work, the orange  text is a compile time error, "Expression 
>> pattern of type 'String' cannot match value of type 'String?'. I realize 
>> that this can be replaced with a let statement (case let s where s == 
>> "Hello, playground":), but that is verbose. 
>> 
>> Seems like the compiler could be OK with the orange text, since it is 
>> clearly not nil.
>> 
>> Thoughts?
>> 
>> -Lucas
>> 
>> 
>> 
>> 
>> 
>> 
>> ___
>> swift-evolution mailing list
>> swift-evolution@swift.org <>
>> https://lists.swift.org/mailman/listinfo/swift-evolution 
>> 
> 
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Re: [swift-evolution] Optionals and nil in Switch statement

[Nevin Brackett-Rozinsky via swift-evolution]

I just got home and tested. The answer is yes, `case "text"?` does work.

let optStr : String? = "text"
switch optStr {
case nil : print("Nil")
case "text"? : print("Success")
default  : print("Default")
}
// Prints `Success`

Nevin

On Tue, Jun 28, 2016 at 12:27 PM, Nevin Brackett-Rozinsky <
nevin.brackettrozin...@gmail.com> wrote:

> Does `case "text"?` work?
>
>
> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution <
> swift-evolution@swift.org> wrote:
>
>> Case .none:
>> Case .some("string"):
>>
>>
>> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution <
>> swift-evolution@swift.org> wrote:
>>
>> Forgive me if this was/is discussed already, I am new to the process
>> here
>>
>> (code is attached as a playground too)
>>
>>
>>
>> Sometimes when I am working with a String? nil can be a reasonable value,
>> and what I want to do is something like the following:
>>
>> import UIKit
>>
>>
>> var str:String? = "Hello, playground"
>>
>>
>> switch str{
>>
>> case nil:
>>
>> print("Nil!")
>>
>> case "Hello, playground":  //it would be super nice if this worked.
>>
>> print("Match")
>>
>> default:
>>
>> print("Some other non nil value?")
>>
>> }
>>
>>
>> But it does not work, the orange  text is a compile time error,
>> "Expression pattern of type 'String' cannot match value of type 'String?'.
>> I realize that this can be replaced with a let statement (case let s
>> where s == "Hello, playground":), but that is verbose.
>>
>> Seems like the compiler could be OK with the orange text, since it is
>> clearly not nil.
>>
>> Thoughts?
>>
>> -Lucas
>>
>>
>>
>>
>>
>> 
>>
>> ___
>> swift-evolution mailing list
>> swift-evolution@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>>
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Re: [swift-evolution] Optionals and nil in Switch statement

[Kevin Nattinger via swift-evolution]

Slight amendment for `let` case, which does evidently still require the 
explicit `.some`

switch str {
case "foo": print("foo")
case .some(let string): print(string) // `case let .some(string)` also works
case nil: print("nil")
}

> On Jun 28, 2016, at 11:10 AM, Kevin Nattinger via swift-evolution 
>  wrote:
> 
> I’ve always thought it’s a bit odd, but that’s the way it is. FWIW, if you 
> define `T? ~= T?` (switch uses `~=` under the hood), you can use that syntax:
> 
> public func ~=(a: T?, b: T?) -> Bool {
>   return a == b
> }
> 
> switch str {
> case "foo": print("foo")
> case "bar": print("bar")
> case nil: print("nil")
> default: print("other")
> }
> 
> For better or worse, this prevents you from using the `.some(x)` / `.none` 
> version.
> 
> You could propose adding this to the standard library to the swift-evolution 
> list, see how they react.
> 
>> On Jun 28, 2016, at 9:52 AM, Lucas Jordan  wrote:
>> 
>> This is sort of weird right? because comparing nil to a non nil string is a 
>> reasonable thing to do:
>> 
>> var nilString:String? = nil
>> 
>> if nilString == "this always fails" {}
>> 
>> is totally reasonable.
>> 
>> On Tue, Jun 28, 2016 at 12:33 PM, Kevin Nattinger  
>> wrote:
>> No
>> 
>>   7> switch str {
>>   8. case "foo": print("case foo")
>>   9. case .none: print("(nil)")
>>  10. }
>> error: repl.swift:8:6: error: value of optional type 'String?' not 
>> unwrapped; did you mean to use '!' or '?'?
>> case "foo": print("case foo")
>>  ^
>>   !
>> Odd error, but at least it suggests it’s an issue with optionaity.
>> 
>> 
>>> On Jun 28, 2016, at 9:27 AM, Nevin Brackett-Rozinsky 
>>>  wrote:
>>> 
>>> Does `case "text"?` work?
>>> 
>>> 
>>> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
>>>  wrote:
>>> Case .none:
>>> Case .some("string"):
>>> 
>>> 
>>> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>>>  wrote:
>>> 
 Forgive me if this was/is discussed already, I am new to the process 
 here
 
 (code is attached as a playground too)
 
 
 
 Sometimes when I am working with a String? nil can be a reasonable value, 
 and what I want to do is something like the following:
 
 import UIKit
 
 
 
 var str:String? = "Hello, playground"
 
 
 
 switch str{
 
 case nil:
 
 print("Nil!")
 
 case "Hello, playground":  //it would be super nice if this worked.
 
 print("Match")
 
 default:
 
 print("Some other non nil value?")
 
 }
 
 
 
 But it does not work, the orange  text is a compile time error, 
 "Expression pattern of type 'String' cannot match value of type 'String?'. 
 I realize that this can be replaced with a let statement (case let s where 
 s == "Hello, playground":), but that is verbose. 
 
 Seems like the compiler could be OK with the orange text, since it is 
 clearly not nil.
 
 Thoughts?
 
 -Lucas
 
 
 
 
 
 
 ___
 swift-evolution mailing list
 swift-evolution@swift.org
 https://lists.swift.org/mailman/listinfo/swift-evolution
>> 
>> 
> 
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Re: [swift-evolution] Optionals and nil in Switch statement

[Kevin Nattinger via swift-evolution]

I’ve always thought it’s a bit odd, but that’s the way it is. FWIW, if you 
define `T? ~= T?` (switch uses `~=` under the hood), you can use that syntax:

public func ~=(a: T?, b: T?) -> Bool {
return a == b
}

switch str {
case "foo": print("foo")
case "bar": print("bar")
case nil: print("nil")
default: print("other")
}

For better or worse, this prevents you from using the `.some(x)` / `.none` 
version.

You could propose adding this to the standard library to the swift-evolution 
list, see how they react.

> On Jun 28, 2016, at 9:52 AM, Lucas Jordan  wrote:
> 
> This is sort of weird right? because comparing nil to a non nil string is a 
> reasonable thing to do:
> 
> var nilString:String? = nil
> 
> if nilString == "this always fails" {}
> 
> is totally reasonable.
> 
> On Tue, Jun 28, 2016 at 12:33 PM, Kevin Nattinger  wrote:
> No
> 
>   7> switch str {
>   8. case "foo": print("case foo")
>   9. case .none: print("(nil)")
>  10. }
> error: repl.swift:8:6: error: value of optional type 'String?' not unwrapped; 
> did you mean to use '!' or '?'?
> case "foo": print("case foo")
>  ^
>   !
> Odd error, but at least it suggests it’s an issue with optionaity.
> 
> 
>> On Jun 28, 2016, at 9:27 AM, Nevin Brackett-Rozinsky 
>>  wrote:
>> 
>> Does `case "text"?` work?
>> 
>> 
>> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
>>  wrote:
>> Case .none:
>> Case .some("string"):
>> 
>> 
>> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>>  wrote:
>> 
>>> Forgive me if this was/is discussed already, I am new to the process 
>>> here
>>> 
>>> (code is attached as a playground too)
>>> 
>>> 
>>> 
>>> Sometimes when I am working with a String? nil can be a reasonable value, 
>>> and what I want to do is something like the following:
>>> 
>>> import UIKit
>>> 
>>> 
>>> 
>>> var str:String? = "Hello, playground"
>>> 
>>> 
>>> 
>>> switch str{
>>> 
>>> case nil:
>>> 
>>> print("Nil!")
>>> 
>>> case "Hello, playground":  //it would be super nice if this worked.
>>> 
>>> print("Match")
>>> 
>>> default:
>>> 
>>> print("Some other non nil value?")
>>> 
>>> }
>>> 
>>> 
>>> 
>>> But it does not work, the orange  text is a compile time error, "Expression 
>>> pattern of type 'String' cannot match value of type 'String?'. I realize 
>>> that this can be replaced with a let statement (case let s where s == 
>>> "Hello, playground":), but that is verbose. 
>>> 
>>> Seems like the compiler could be OK with the orange text, since it is 
>>> clearly not nil.
>>> 
>>> Thoughts?
>>> 
>>> -Lucas
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> ___
>>> swift-evolution mailing list
>>> swift-evolution@swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
> 
> 

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Re: [swift-evolution] Optionals and nil in Switch statement

[Lucas Jordan via swift-evolution]

This is sort of weird right? because comparing nil to a non nil string is a
reasonable thing to do:

var nilString:String? = nil

if nilString == "this always fails" {}

is totally reasonable.

On Tue, Jun 28, 2016 at 12:33 PM, Kevin Nattinger 
wrote:

> No
>
>   7> switch str {
>   8. case "foo": print("case foo")
>   9. case .none: print("(nil)")
>  10. }
> error: repl.swift:8:6: error: value of optional type 'String?' not
> unwrapped; did you mean to use '!' or '?'?
> case "foo": print("case foo")
>  ^
>   !
> Odd error, but at least it suggests it’s an issue with optionaity.
>
>
> On Jun 28, 2016, at 9:27 AM, Nevin Brackett-Rozinsky <
> nevin.brackettrozin...@gmail.com> wrote:
>
> Does `case "text"?` work?
>
>
> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution <
> swift-evolution@swift.org> wrote:
> Case .none:
> Case .some("string"):
>
>
> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution <
> swift-evolution@swift.org> wrote:
>
> Forgive me if this was/is discussed already, I am new to the process
> here
>
> (code is attached as a playground too)
>
>
>
> Sometimes when I am working with a String? nil can be a reasonable value,
> and what I want to do is something like the following:
>
> import UIKit
>
>
>
> var str:String? = "Hello, playground"
>
>
>
> switch str{
>
> case nil:
>
> print("Nil!")
>
> case "Hello, playground":  //it would be super nice if this worked.
>
> print("Match")
>
> default:
>
> print("Some other non nil value?")
>
> }
>
>
>
> But it does not work, the orange  text is a compile time error,
> "Expression pattern of type 'String' cannot match value of type 'String?'.
> I realize that this can be replaced with a let statement
> (case let s where s == "Hello, playground":), but that is verbose.
>
> Seems like the compiler could be OK with the orange text, since it is
> clearly not nil.
>
> Thoughts?
>
> -Lucas
>
>
>
>
>
> 
>
> ___
> swift-evolution mailing list
> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
>
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Re: [swift-evolution] Optionals and nil in Switch statement

[Kevin Nattinger via swift-evolution]

No

  7> switch str {
  8. case "foo": print("case foo")
  9. case .none: print("(nil)")
 10. }
error: repl.swift:8:6: error: value of optional type 'String?' not unwrapped; 
did you mean to use '!' or '?'?
case "foo": print("case foo")
 ^
  !
Odd error, but at least it suggests it’s an issue with optionaity.

> On Jun 28, 2016, at 9:27 AM, Nevin Brackett-Rozinsky 
>  wrote:
> 
> Does `case "text"?` work?
> 
> 
> On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution 
>  wrote:
> Case .none:
> Case .some("string"):
> 
> 
> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>  wrote:
> 
>> Forgive me if this was/is discussed already, I am new to the process here
>> 
>> (code is attached as a playground too)
>> 
>> 
>> 
>> Sometimes when I am working with a String? nil can be a reasonable value, 
>> and what I want to do is something like the following:
>> 
>> import UIKit
>> 
>> 
>> 
>> var str:String? = "Hello, playground"
>> 
>> 
>> 
>> switch str{
>> 
>> case nil:
>> 
>> print("Nil!")
>> 
>> case "Hello, playground":  //it would be super nice if this worked.
>> 
>> print("Match")
>> 
>> default:
>> 
>> print("Some other non nil value?")
>> 
>> }
>> 
>> 
>> 
>> But it does not work, the orange  text is a compile time error, "Expression 
>> pattern of type 'String' cannot match value of type 'String?'. I realize 
>> that this can be replaced with a let statement (case let s where s == 
>> "Hello, playground":), but that is verbose. 
>> 
>> Seems like the compiler could be OK with the orange text, since it is 
>> clearly not nil.
>> 
>> Thoughts?
>> 
>> -Lucas
>> 
>> 
>> 
>> 
>> 
>> 
>> ___
>> swift-evolution mailing list
>> swift-evolution@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution

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Re: [swift-evolution] Optionals and nil in Switch statement

[Nevin Brackett-Rozinsky via swift-evolution]

Does `case "text"?` work?


On Tuesday, June 28, 2016, Kevin Nattinger via swift-evolution <
swift-evolution@swift.org> wrote:

> Case .none:
> Case .some("string"):
>
>
> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution <
> swift-evolution@swift.org
> > wrote:
>
> Forgive me if this was/is discussed already, I am new to the process
> here
>
> (code is attached as a playground too)
>
>
>
> Sometimes when I am working with a String? nil can be a reasonable value,
> and what I want to do is something like the following:
>
> import UIKit
>
>
> var str:String? = "Hello, playground"
>
>
> switch str{
>
> case nil:
>
> print("Nil!")
>
> case "Hello, playground":  //it would be super nice if this worked.
>
> print("Match")
>
> default:
>
> print("Some other non nil value?")
>
> }
>
>
> But it does not work, the orange  text is a compile time error,
> "Expression pattern of type 'String' cannot match value of type 'String?'.
> I realize that this can be replaced with a let statement (case let s where
> s == "Hello, playground":), but that is verbose.
>
> Seems like the compiler could be OK with the orange text, since it is
> clearly not nil.
>
> Thoughts?
>
> -Lucas
>
>
>
>
>
> 
>
> ___
> swift-evolution mailing list
> swift-evolution@swift.org
> 
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
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Re: [swift-evolution] Optionals and nil in Switch statement

[Kevin Nattinger via swift-evolution]

Case .none:
Case .some("string"):


> On Jun 28, 2016, at 06:40, Lucas Jordan via swift-evolution 
>  wrote:
> 
> Forgive me if this was/is discussed already, I am new to the process here
> 
> (code is attached as a playground too)
> 
> 
> 
> Sometimes when I am working with a String? nil can be a reasonable value, and 
> what I want to do is something like the following:
> 
> import UIKit
> 
> 
> 
> var str:String? = "Hello, playground"
> 
> 
> 
> switch str{
> 
> case nil:
> 
> print("Nil!")
> 
> case "Hello, playground":  //it would be super nice if this worked.
> 
> print("Match")
> 
> default:
> 
> print("Some other non nil value?")
> 
> }
> 
> 
> 
> But it does not work, the orange  text is a compile time error, "Expression 
> pattern of type 'String' cannot match value of type 'String?'. I realize that 
> this can be replaced with a let statement (case let s where s == "Hello, 
> playground":), but that is verbose. 
> 
> Seems like the compiler could be OK with the orange text, since it is clearly 
> not nil.
> 
> Thoughts?
> 
> -Lucas
> 
> 
> 
> 
> 
> 
> ___
> swift-evolution mailing list
> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
___
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