[swift-users] Nil coalescing operator (??) and function vars

[davesweeris at mac.com]

Looks like a bug to me.

You can work around it either by substituting the long version:
let fn:(String) -> String = x != nil ? x! : qq
or by declaring qq & fn like this:
let qq:(String -> String)? = { _ in return "..." }
let fn:String -> String = (x ?? qq)!
or like this:
let qq:(String -> String)! = { _ in return "..." }
let fn:String -> String = x ?? qq

Hope that helps.

- Dave Sweeris

> On Apr 18, 2016, at 1:42 PM, Peter Eddy via swift-users <swift-users at swift.org> wrote:
> 
> Hello,
> 
> I'd like to understand why I'm unable to use the nil coalescing operator with functions.
> 
> For example, I'd like to write a function that takes an optional function as a parameter and that uses the nil coalescing operator to select a default function if the function's  function parameter is nil, e.g:
> 
>     func test(x: ((String) -> String)? = nil) {
> 
>       let qq = { (p:String) -> String in return "..." }
> 
>       let fn: String -> String = x ?? qq
> 
>       fn("test")
>     }
> 
> When I do this the compiler complains that:
> 
>   Binary operator '??' cannot be applied to operands of type '((String) -> String)?' and '(String) -> String:
> 
> In the Swift 2.2 Language Guide (https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/BasicOperators.html <https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/BasicOperators.html>) it states:
> 
> The nil coalescing operator is shorthand for the code below:
> 
> a != nil ? a! : b
> If I use the longhand option then the complier's fine:
> 
>     func test(x: ((String) -> String)? = nil)  {
>   
>         let qq = { (p:String) -> String in return "..." }
>   
>         let fn = x != nil ? x! : qq
> 
>         fn("test")
>     }
> 
> So why doesn't the nil coalescing operator work for function vars? 
> 
> thanks!
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> swift-users at swift.org
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