[swift-evolution] Shorthand unwrap proposal

[L. Mihalkovic]

Regards
LM
(From mobile)

> On Jun 24, 2016, at 2:50 PM, Charlie Monroe via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Yes, this is a bit different. There was a discussion about a month ago (http://thread.gmane.org/gmane.comp.lang.swift.evolution/17142) which had a few good ideas how to deal with the following pattern:
> 
> if let x = x { // do something with x }
> guard let x = x { return }
> 

For my own education i built

if let! x {
// x is shadowed
}


> which is shadowing the original optional value. The suggestion was:
> 
> if let x! { // within this block, x is no longer optional }
> 
> guard let x! { return }
> // Now x is no longer an optional.
> 
> Generally, it re-used the same variable name to safe-unwrap the optional. In your particular example:
> 
> let i: Int? = nil
> if let i! {
> 	let y = i.toIntMax()
> 	/// ...
> }
> 
> I am aware of the .map (or flatMap) on the optional, however, the guard statement in particular seems like an improvement.
> 
> There are many language constructs in Swift that can be expressed using other constructs - you can go all the way down and say that you really don't need anything other than if and goto.
> 
> The question is whether such a syntax sugar is something that would be help one write safer code and if it's something people would use.
> 
> 
>> On Jun 23, 2016, at 9:32 PM, David Sweeris <davesweeris at mac.com> wrote:
>> 
>> Dmitri pointed out a few posts ago that Swift already has this.
>> let opInt: Int? = nil
>> opInt.map {$0.toIntMax()} //Evaluates to nil
>> 
>> Are you talking about something different?
>> 
>> - Dave Sweeris
>> 
>>> On Jun 23, 2016, at 2:04 PM, Charlie Monroe via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> Sure, the exact syntax is a matter of discussion, I just wasn't that much of favor of the very short
>>> 
>>> doSomething(with: myOptional?)
>>> 
>>> - it looks like a great idea, making the code really short
>>> - on the other hand the question mark is next to the variable, but the method's execution is optional - in that sense something like doSomething(?: myOptional)(with: myOptional) makes more sense, declaring explicitely what optionals does the execution depend on.
>>> - nevertheless, in the interest of clarity and readability of the code, I'm still in favor of the original proposal, which requires you to either use if or guard.
>>> 
>>>> On Jun 23, 2016, at 8:57 PM, Tim Vermeulen <tvermeulen at me.com> wrote:
>>>> 
>>>> But ! still suggests force unwrapping, while ? suggests safe unwrapping. Why not use a question mark?
>>>> 
>>>>> It was in the previous proposal and suggested that you are not trying to shadow the previous variable, but trying to unwrap it - and it acts as unwrapped from there on.
>>>>> 
>>>>> 
>>>>>> On Jun 23, 2016, at 8:52 PM, Tim Vermeulen<tvermeulen at me.com>wrote:
>>>>>> 
>>>>>> Why with the exclamation mark? It suggests you’re force unwrapping something.
>>>>>> 
>>>>>>>> On Jun 23, 2016, at 8:45 PM, Tim Vermeulen via swift-evolution<swift-evolution at swift.org>wrote:
>>>>>>>> 
>>>>>>>> I would love to be able to do something like
>>>>>>>> 
>>>>>>>> doSomething(with: myOptional?)
>>>>>>> This actually looks good to me, though if I were a newcomer to the language, it would be really cryptic.
>>>>>>> 
>>>>>>> In case the function returned any value, it could become an optional, just like with try?...
>>>>>>> 
>>>>>>> I still, however, prefer the original proposal of if let myOptional! { doSomething(myOptional) }...
>>>>>>> 
>>>>>>>> 
>>>>>>>> which would be equivalent to
>>>>>>>> 
>>>>>>>> if let myValue = myOptional {
>>>>>>>> doSomething(with: myValue)
>>>>>>>> }
>>>>>>>> 
>>>>>>>> But it’s been discussed here before, and I don’t think people were very enthusiastic about it.
>>>>>>>> 
>>>>>>>>> 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(mailto:james at supmenow.com)⎥supmenow.com(http://supmenow.com)
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Sup
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Runway East
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 10 Finsbury Square
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> London
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> EC2A 1AF
>>>>>>>> _______________________________________________
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>>>>>>>> swift-evolution at swift.org
>>>>>>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> 
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