Open Radar

 
Summary:
Object is overreleased under special conditions

Steps to Reproduce:
Run attached code and execute buttonBreakObjectPressed.

Expected Results:
testObject variable is not deallocated.

Actual Results:
testObject constant is deallocated still being strongly referenced by MainViewController.

Version:
10.3

Notes:
There is slight difference between Holder’s getObject and getCrashingObject methods - last one is contained inside switch case block.
To reproduce this issue, few things required: 
- TestProtocol must be class
- TestClass must be NSObject descendant.


class Holder {
    fileprivate weak var reference: AnyObject?
    
    init(reference: AnyObject) {
        self.reference = reference
    }
    
    func getObject<T>() -> T? {
        return self.reference as? T
    }
    
    func getCrashingObject<T>() -> T? {
        switch (self.reference) {
            case is T:
                return self.reference as? T
            default:
                return nil
        }
    }
}

public protocol TestProtocol: class {
    func foo()
}

class TestClass: NSObject, TestProtocol {
    deinit {
        print("TestClass deinit!")
    }

    func foo() {
        
    }
}

class MasterViewController: UIViewController {
    
    let testObject = TestClass()
    
    @IBAction func buttonBreakObjectPressed() {
        print("buttonBreakObjectPressed")
        
        let holder = Holder(reference: self.testObject)
        
        guard let testProtocol: TestProtocol = holder.getCrashingObject() else {
            return
        }
        
        testProtocol.foo()
    }
    
    @IBAction func buttonUseObjectPressed() {
        print("buttonUseObjectPressed")
        
        let holder = Holder(reference: self.testObject)
        
        guard let testProtocol: TestClass = holder.getObject() else {
            return
        }
        
        testProtocol.foo()
    }
}