Hi Matthew,
Finally found time to read the proposal. Much better than the previous
iterration. I’m not a huge fan of the proposed syntax either but don’t have the
energy for bike shedding :)
As a side note, I’d like to say that I would not use this very often. I much
more often use unowned capture variables when its clear that the closure can’t
outlive the captured variable. For example, my code often looks like this:
class MyViewController : UIViewController {
var button: ActionButton!
override func viewDidLoad() {
super.viewDidLoad()
button.addAction { [unowned self] in
print("self: \(self)")
}
}
}
> On 20 Feb 2017, at 18:01, Matthew Johnson via swift-evolution
> <swift-evolution@swift.org> wrote:
>
>
>> On Feb 20, 2017, at 8:33 AM, Florent Bruneau <florent.brun...@intersec.com>
>> wrote:
>>
>>
>>
>>> Le 20 févr. 2017 à 06:35, Brent Royal-Gordon via swift-evolution
>>> <swift-evolution@swift.org> a écrit :
>>>
>>>> On Feb 19, 2017, at 2:57 PM, Matthew Johnson via swift-evolution
>>>> <swift-evolution@swift.org> wrote:
>>>>
>>>> A guarded closure may be created by prefixing a bound instance method
>>>> reference with the `?` sigil:
>>>>
>>>> ```swift
>>>> let guarded = ?myObject.myMethod
>>>>
>>>> // desugars to:
>>>> let guarded = { [weak myObject] in
>>>> guard let myObejct = myObject else {
>>>> return
>>>> }
>>>> myObject.myMethod()
>>>> }
>>>> ```
>>>
>>> I like this in principle, but I don't like the syntax. The `?` is cryptic
>>> and looks pretty strange in prefix position. I think what I'd like to see
>>> is:
>>>
>>> let guarded = weak myObject.myMethod
>>
>> I like the idea of weak closures even if this may conflict with the fact
>> closures are already internally refcounted object. While we cannot have weak
>> references to closure in the language, using `weak` might be misleading in
>> some ways.
>>
>> In term of syntax, the `weak` keyword looks nice (much better than the '?'
>> and @guarded once). The weak could be used on both sides.
>>
>> ```swift
>> addAction(action: weak Action)
>> addAction(action: weak myAction)
>> ```
>>
>> However, I think this might still look weird with inlined closures, in
>> particular in case you use the suffix syntax for closures:
>>
>> ```swift
>> addAction() weak {
>> /* */
>> }
>> ```
>
>
> We wouldn’t want to use `weak` if this has the guarded behavior I proposed.
> We could use `guarded` though.
>
> There are a couple of important things enabled by having the language
> implement the guarded behavior.
>
> First, the implementation could release the entire closure context as soon as
> one of the guarded captures is released. This is not possible if users write
> the code out manually. Second, in the future directions I discuss allowing
> libraries to detect that the guard has been triggered and the closure has
> become a no-op. This is also not possible when users write the guard out
> manually and would be quite desirable for libraries that want to discard
> their reference to the closure after it becomes a no-op.
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
