CODEWITHSUNDEEP
macosdelegatesswift
George
George

Reputation: 1255

Swift weak delegate runtime error (bad access). Bug?

I have a problem with delegates in Swift (OSX). I have a view, connected to a delegate through a weak reference. Simplified code could be like this:

protocol MyProtocol: class {
    func protocolFunc() -> Int
}

class MyController : MyProtocol {
    func protocolFunc() -> Int { return 2 }
}

class MyView : NSView {
    weak var delegate: MyProtocol?

    func grabData {
        var data = delegate?.protocolFunc()
    }
}

When delegate?.protocolFunc() is called, the app crashes saying "bad access". It's like if the MyController instance had disappeared... But it has not. The MyController instance lives in a NSDocument subclass; and view's delegate is properly set.

The crash goes away if I declare the delegate to be strong. But the thing is I want the delegate to be weak. What's going on? To my eyes, the weak reference should work.

Upvotes: 0

Views: 434

Answers (2)

Scott Mielcarski
Scott Mielcarski

Reputation: 760

A temporary alternate solution would be to change this:

weak var delegate: MyProtocol?

to this:

weak var delegate: MyController?

Of course it defeats the purpose of MyProtocol, however, it allows you to use pure Swift classes while we wait for a proper fix for this.

Upvotes: 0

Kamaros
Kamaros

Reputation: 4566

At the time of writing (Xcode 6 Beta 5), there's a bug with weak delegates. For the time being, all you can do until it is fixed is to change protocol MyProtocol: class to @objc protocol MyProtocol and avoid using any pure Swift classes in your protocol.

Upvotes: 1

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