[swift-evolution] Shorthand unwrap proposal

[L. Mihalkovic]

You can also do something like that is ur code today:

extension Optional {
    func unwrap<T> (_ h: T -> ()) {
        switch self {
        case .Some(let w):
            if let t = w as? T { h(t) }
            break
        default:
            break;
        }
    }
}

s1.unwrap { (str:String) in
    print("NOPE")  // nothing happens
}
s2.unwrap { (str:String) in
    print(":)")          // prints
}


Regards
(From mobile)

> On Jun 23, 2016, at 6:25 PM, James Campbell via swift-evolution <swift-evolution at swift.org> wrote:
> 
> So if the function I run inside of the map has a return value of Void will that still compile ?
> 
> ___________________________________
> 
> James⎥Head of Trolls
> 
> james at supmenow.com⎥supmenow.com
> 
> Sup
> 
> Runway East
> 
> 
> 10 Finsbury Square
> 
> London
> 
> 
> EC2A 1AF 
> 
> 
>> On 23 June 2016 at 17:22, Jordan Rose <jordan_rose at apple.com> wrote:
>> I think we’d still just recommend using ‘map’ for this. The reason Collection.map and Collection.forEach are different is because we don’t promise eager and in-order evaluation for Collection.map. But Optional only executes the closure one or zero times, so there’s no ambiguity.
>> 
>> Jordan
>> 
>> 
>>> On Jun 23, 2016, at 09:15, James Campbell via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> So I have a real-life situation in an application, which does what you mention:
>>> 
>>> This code is for a camera app, on a `didSet` it removes a device if set from the capture session, and if there is a new one set it adds it to the capture session.
>>> 
>>> The add and remove methods indeed don't take optionals.
>>> 
>>> So this is the code before:
>>> 
>>> var audioDevice: AVCaptureDeviceInput? = nil {
>>> 
>>>         
>>>         willSet {
>>> 
>>>             if let audioDevice = audioDevice {
>>> 
>>>                captureSession?.removeInput(audioDevice)
>>> 
>>>             }
>>> 
>>>         }
>>> 
>>>         
>>>         didSet {
>>> 
>>>             if audioDevice = audioDevice {
>>> 
>>>                captureSession?.addInput(audioDevice)
>>> 
>>>             }
>>> 
>>>         }
>>> 
>>>     }
>>> 
>>> 
>>> 
>>> and after:
>>> 
>>> var audioDevice: AVCaptureDeviceInput? = nil {
>>> 
>>>         
>>>         willSet {
>>> 
>>>             audioDevice.unwrap {
>>> 
>>>                 self.captureSession?.removeInput($0)
>>> 
>>>             }
>>> 
>>>         }
>>> 
>>>         
>>>         didSet {
>>> 
>>>             audioDevice.unwrap {
>>> 
>>>                 self.captureSession?.addInput($0)
>>> 
>>>             }
>>> 
>>>         }
>>> 
>>>     }
>>> 
>>> 
>>> 
>>> The last two saved me a lot of typing in these cases and I feel like it is more clear what is going on due to the `unwrap` method being clear in it's intent and the lack of `audioDevice` being repeated multiple times.
>>> 
>>> 
>>> ___________________________________
>>> 
>>> James⎥Head of Trolls
>>> 
>>> james at supmenow.com⎥supmenow.com
>>> 
>>> Sup
>>> 
>>> Runway East
>>> 
>>> 
>>> 10 Finsbury Square
>>> 
>>> London
>>> 
>>> 
>>> EC2A 1AF 
>>> 
>>> 
>>>> On 23 June 2016 at 17:11, Sean Heber <sean at fifthace.com> wrote:
>>>> I’m a bit tore on this myself. I see the appeal, but let’s say we had such a function. If you wanted to use it with an named parameter it’d look like this:
>>>> 
>>>> myReallyLongOptionalName.unwrap { string in
>>>>   doSomethingWith(string)
>>>> }
>>>> 
>>>> And that is actually *more* characters than the current approach:
>>>> 
>>>> if let string = myReallyLongOptionalName {
>>>>   doSomethingWith(string)
>>>> }
>>>> 
>>>> However it’d be a big win especially when you can skip $0 and the braces entirely such as:
>>>> 
>>>> myReallyLongOptionalName.unwrap(doSomethingWith)
>>>> 
>>>> Of course if we were dealing with methods, you could write this like:
>>>> 
>>>> myReallyLongOptionalName?.doSomething()
>>>> 
>>>> And that is probably hard to beat.
>>>> 
>>>> So I think the problem really only presents itself when you have an optional that you need to unwrap and use as a parameter to something that does not take an optional.
>>>> 
>>>> I don’t have a solution - just trying to clarify the situation. :)
>>>> 
>>>> l8r
>>>> Sean
>>>> 
>>>> 
>>>> > On Jun 23, 2016, at 10:36 AM, James Campbell via swift-evolution <swift-evolution at swift.org> wrote:
>>>> >
>>>> > I was wondering if people would be open to adding an unwrap method to the Optional type,  I already have a method like this which shortens code for me.
>>>> >
>>>> > So this:
>>>> >
>>>> > let myReallyLongOptionalName: String? = "Hey"
>>>> >
>>>> > if let string = myReallyLongOptionalName {
>>>> >   doSomethingWith(string)
>>>> > }
>>>> >
>>>> > Could become"
>>>> >
>>>> > let myReallyLongOptionalName: String? = "Hey"
>>>> >
>>>> > myReallyLongOptionalName.unwrap {
>>>> >   doSomethingWith($0)
>>>> > }
>>>> >
>>>> > The block would only be fired if myReallyLongOptionalName has a value.
>>>> >
>>>> > ___________________________________
>>>> >
>>>> > James⎥Head of Trolls
>>>> >
>>>> > james at supmenow.com⎥supmenow.com
>>>> >
>>>> > Sup
>>>> >
>>>> > Runway East
>>>> >
>>>> >
>>>> > 10 Finsbury Square
>>>> >
>>>> > London
>>>> >
>>>> > > EC2A 1AF
>>>> >
>>>> > _______________________________________________
>>>> > swift-evolution mailing list
>>>> > swift-evolution at swift.org
>>>> > https://lists.swift.org/mailman/listinfo/swift-evolution
>>> 
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> 
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