Re: [swift-users] ?? operator question
Thanks for your explanation. I still think the compiler should not be that smart, causing only itself could understanding what is going on. It will be a nightmare. Owen On Tue, Apr 19, 2016 at 7:09 PM, Marco Feltmann via swift-users < swift-users@swift.org> wrote: > Just guessed since I try to separate Swift from Objective-C frameworks. > > Am 19.04.2016 um 03:15 schrieb zh ao: > >> I don't think NSNumber is OK here. As t1 is a struct not a literal value. >> > In fact t1 in an OPTIONAL struct. > That means it can point to anything from `nil` to Int Struct, NSInteger > and NSNumber. > AFAIR it automatically bridges to NSNumber as soon as you import > Foundation or a similiar framework. Same works with String. String is a > struct used in plain Swift and NSString used with Foundation. > >> If NSNumber is OK. I think the compiler is too smart than it should be. >> > Indeed it is. Way to smart. > It is that smart that it sometimes stands in its own way. > At least when used with Objective-C. Your question outlines one of those > strange side effects. > >> Also, you should aware that right side of let y works in print(), but does >> not work in let, which is not consistent somehow. >> > It is consistent. > You can map an OPTIONAL integer to NSNumber (using Foundation framework) > but you cannot map an OPTIONAL integer to NSString. > > "But wait a sec, how can NSFount(name: "", size: 0) result in an > NSNumber?" you may ask. > I don't now. > The behaviour of NSFonts +fonttWithName:size: for empty/not found font > name is not defined in the documentation, so ANY result is correct. > > ___ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users > ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
> On Apr 19, 2016, at 4:09 AM, Marco Feltmann via swift-users >wrote: > > "But wait a sec, how can NSFount(name: "", size: 0) result in an NSNumber?" > you may ask. > I don't now. > The behaviour of NSFonts +fonttWithName:size: for empty/not found font name > is not defined in the documentation, so ANY result is correct. That’s not true. The result has to be an NSFont? as declared in the class interface — it can’t be an NSNumber. This has nothing to do with whether the font is not found at runtime; we’re talking about compile-time type inference. —Jens___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
Just guessed since I try to separate Swift from Objective-C frameworks. Am 19.04.2016 um 03:15 schrieb zh ao: I don't think NSNumber is OK here. As t1 is a struct not a literal value. In fact t1 in an OPTIONAL struct. That means it can point to anything from `nil` to Int Struct, NSInteger and NSNumber. AFAIR it automatically bridges to NSNumber as soon as you import Foundation or a similiar framework. Same works with String. String is a struct used in plain Swift and NSString used with Foundation. If NSNumber is OK. I think the compiler is too smart than it should be. Indeed it is. Way to smart. It is that smart that it sometimes stands in its own way. At least when used with Objective-C. Your question outlines one of those strange side effects. Also, you should aware that right side of let y works in print(), but does not work in let, which is not consistent somehow. It is consistent. You can map an OPTIONAL integer to NSNumber (using Foundation framework) but you cannot map an OPTIONAL integer to NSString. "But wait a sec, how can NSFount(name: "", size: 0) result in an NSNumber?" you may ask. I don't now. The behaviour of NSFonts +fonttWithName:size: for empty/not found font name is not defined in the documentation, so ANY result is correct. ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
I don't think NSNumber is OK here. As t1 is a struct not a literal value. If NSNumber is OK. I think the compiler is too smart than it should be. Also, you should aware that right side of let y works in print(), but does not work in let, which is not consistent somehow. Owen On Mon, Apr 18, 2016 at 9:49 PM, Erica Sadunwrote: > > On Apr 18, 2016, at 7:23 AM, zh ao via swift-users > wrote: > > I do think there is something wrong here. > > // Xcode 7.3.1, Swift 2.2 > > let t1: Int? = 2 // struct Int? > let y = t1 ?? "abcdf" // error > let x = t1 ?? NSFont(name: "", size: 0) // x: NSObject? > > for x, how could it be NSObject?, as t1 is a struct? > > zhaoxin > > > My guess would be NSNumber. > > Strings can bridge to NSString (struct to class), enums of ErrorType to > NSError (enum to class), etc. > > -- E > > ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
Swift will infer types from the context of an expression as well as the inputs. In this case, although 'Int' and 'String' do not share a type, they are both convertible to 'Any', the argument to 'print'. So because of the call to 'print', 'T' becomes 'Any', and the expression becomes, essentially print((t1 as Any?) ?? ("asdf" as Any)) (Actually, the signature of 'print' is a little more complicated than that, but that's the gist of what's going on.) Jordan > On Apr 18, 2016, at 2:51, tuuranton--- via swift-users >wrote: > > Why does this compile? > > let t1: Int? = 2 > print(t1 ?? "asdf") > > The type of ?? is this: > > @warn_unused_result > public func ??(optional: T?, @autoclosure defaultValue: () throws -> T) > rethrows -> T > > The type syas that T must be the same type throughout. But above I could > successfully use Int? and then String. Why? > ___ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
> On Apr 18, 2016, at 7:23 AM, zh ao via swift-users> wrote: > > I do think there is something wrong here. > > // Xcode 7.3.1, Swift 2.2 > > let t1: Int? = 2 // struct Int? > let y = t1 ?? "abcdf" // error > let x = t1 ?? NSFont(name: "", size: 0) // x: NSObject? > > for x, how could it be NSObject?, as t1 is a struct? > > zhaoxin My guess would be NSNumber. Strings can bridge to NSString (struct to class), enums of ErrorType to NSError (enum to class), etc. -- E ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
I do think there is something wrong here. // Xcode 7.3.1, Swift 2.2 let t1: Int? = 2 // struct Int? let y = t1 ?? "abcdf" // error let x = t1 ?? NSFont(name: "", size: 0) // x: NSObject? for x, how could it be NSObject?, as t1 is a struct? zhaoxin On Mon, Apr 18, 2016 at 6:59 PM, Marco Feltmann via swift-users < swift-users@swift.org> wrote: > Am 18.04.2016 um 11:51 schrieb tuuranton--- via swift-users: > > Why does this compile? > let t1: Int? = 2print(t1 ?? "asdf") > > Well, I guess you try to re-typedef (??) a language construct. > According to NSHipster ?? is the languages nil coalescing operator. > > So it simply compiles because t1 isn't nil. > > Further reference: > https://en.wikipedia.org/wiki/Null_coalescing_operator#Swift > > ___ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users > > ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
Am 18.04.2016 um 11:51 schrieb tuuranton--- via swift-users: Why does this compile? let t1: Int? = 2print(t1 ?? "asdf") Well, I guess you try to re-typedef (??) a language construct. According to NSHipster ?? is the languages |nil| coalescing operator. So it simply compiles because t1 isn't nil. Further reference: https://en.wikipedia.org/wiki/Null_coalescing_operator#Swift ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] ?? operator question
Because in your example T = CustomStringConvertible On Mon, Apr 18, 2016 at 10:51 AM, tuuranton--- via swift-users < swift-users@swift.org> wrote: > Why does this compile? > > let t1: Int? = 2 > print(t1 ?? "asdf") > > The type of ?? is this: > > @warn_unused_result > public func ??(optional: T?, @autoclosure defaultValue: () throws -> T) > rethrows -> T > > The type syas that T must be the same type throughout. But above I could > successfully use Int? and then String. Why? > > ___ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users > > -- Marius Serban ___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
[swift-users] ?? operator question
Why does this compile? let t1: Int? = 2print(t1 ?? "asdf") The type of ?? is this: @warn_unused_resultpublic func ??(optional: T?, @autoclosure defaultValue: () throws -> T) rethrows -> T The type syas that T must be the same type throughout. But above I could successfully use Int? and then String. Why?___ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users