All func pointers need a protocol now?

Question

I'm trying to do this simple callback method:

final class MyView: UIView {
    var onSomeAction: ((String) -> Void)!
}

final class MyViewController: UIViewController {
    let myView = MyView(frame: CGRectZero)
    override func viewDidLoad() {
        super.viewDidLoad()
        myView.onSomeAction = someFunc
    }

    private func someFunc(str: String) {
    }
}

But that's going to create a retain cycle (I believe). I can't just mark the onSomeAction var as weak because that's a compile time error.

Do I really need to go to the level of defining a protocol for this just so I can mark it as a class protocol and then mark that callback to be a weak reference?

I've gotta be missing something here.

Swift

1k

Posted by

Gargoyle

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Answer 1

var onSomeAction_get: () -> (String -> Void)! = {nil}

myView.onSomeAction_get = {[unowned self] in self.someFunc}

Posted by

Jessy

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Answer 2

var onSomeAction_get: () -> (String -> Void)! = {nil}

myView.onSomeAction_get = {[unowned self] in self.someFunc}

Posted by

Jessy

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Answer 3

That doesn't really make sense. You're still capturing a strong reference in MyView. Your [unowned self] just says that the closure itself won't capture itself strongly.

Posted by

Gargoyle

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Answer 4

Fixed. Sorry. Tired.

This is one of my use cases for mutable property accessors.

Posted by

Jessy

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Answer 5

So, what's your take? This is what I've been using as a replacement for delegates, except with weak instead of unowned.

Posted by

Jessy

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Answer 6

It definitely has to be weak, and I think it would work. Just feels a bit like a missing language feature. It's too easy to just assign a function to a property like this and think things are OK, only to later realize you've made a retain cycle. We should somehow be able to tell Swift that the pointer to the closure should always be weak without needing a protocol for it.

Posted by

Gargoyle

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Answer 7

I agree.

And as for mutable accessors, here's what I use when both get and set need to be mutable:

https://github.com/Catterwaul/HemiprocneMystacea/blob/master/HemiprocneMystacea/Swift/Properties/Mutable%20Properties.swift

What I want this to look like is this:

weak var onSomeAction: (String -> Void)?
myView.onSomeAction get = {[weak self] in self?.someFunc}

Posted by

Jessy

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All func pointers need a protocol now?

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