Open Radar

 
If I have a protocol, and an object that conforms to that protocol, and I have another object that has an unowned reference to an object conforming to that protocol, after setting that reference in init, accessing it crashes my app. 

So.

That's a protocol:

@objc protocol MyProtocol: NSObjectProtocol {
    func method() -> ()
}

And an object conforming to that protocol:

class DelegateClass: NSObject, MyProtocol {
    func method () {
        for i in 1...10 {
            "Hello!"
        }
    }
}

So far so good. Then I have an object that has a reference to an object conforming to that protocol which is unowned. 

class MyObject : NSObject {
    unowned let delegate: MyProtocol
    
    init(delegate: MyProtocol) {
        self.delegate = delegate
        super.init()
    }
    
    func doSomethingWithDelegate() {
        delegate.method()
    }
}

OK, cool. Now let's set some instances up:

let delegate = DelegateClass()
let object = MyObject(delegate: delegate)

And try and access the delegate:

object.doSomethingWithDelegate()

Crash. 

* thread #1: tid = 0x8f817d, 0x001ba570 libswift_stdlib_core.dylib`_swift_release_slow, queue = 'com.apple.main-thread', stop reason = EXC_BREAKPOINT (code=EXC_I386_BPT, subcode=0x0)
    frame #0: 0x001ba570 libswift_stdlib_core.dylib`_swift_release_slow
    frame #1: 0xbfffcf98
    frame #2: 0x001c8f7e libswift_stdlib_core.dylib`swift_unknownRetainUnowned + 318
    frame #3: 0x00003470 Bug`@objc Bug.MyObject.delegate.getter : @unowned Bug.MyProtocol + 64 at AppDelegate.swift:0
  * frame #4: 0x0000364c Bug`Bug.MyObject.doSomethingWithDelegate (self=0x0b20ff70)() -> () + 60 at AppDelegate.swift:29
    frame #5: 0x000036c2 Bug`@objc Bug.MyObject.doSomethingWithDelegate (Bug.MyObject)() -> () + 34 at AppDelegate.swift:0
    frame #6: 0x00003e95 Bug`Bug.AppDelegate.application (application=0x018fe804, launchOptions=None, self=0x0b500040)(ObjectiveC.UIApplication, didFinishLaunchingWithOptions : Swift.Optional<ObjectiveC.NSDictionary>) -> Swift.Bool + 149 at AppDelegate.swift:56
    frame #7: 0x00003f55 Bug`@objc Bug.AppDelegate.application (Bug.AppDelegate)(ObjectiveC.UIApplication, didFinishLaunchingWithOptions : Swift.Optional<ObjectiveC.NSDictionary>) -> Swift.Bool + 101 at AppDelegate.swift:0
    frame #8: 0x00c44b37 UIKit`-[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 291
    frame #9: 0x00c45875 UIKit`-[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2920
    frame #10: 0x00c48a33 UIKit`-[UIApplication _runWithMainScene:transitionContext:completion:] + 1507
    frame #11: 0x00c60eb8 UIKit`__84-[UIApplication _handleApplicationActivationWithScene:transitionContext:completion:]_block_invoke + 59
    frame #12: 0x00c4777e UIKit`-[UIApplication workspaceDidEndTransaction:] + 29
    frame #13: 0x03404f1f FrontBoardServices`-[FBSWorkspace clientEndTransaction:] + 87
    frame #14: 0x0340c4ed FrontBoar


Source: http://cloud.ashfurrow.com/1h05282t000X