Question

我有以下结构

Main ViewController：它负责调用（A）视图控制器。（A）ViewController：创建一个CustomClass实例并具有该类的委托。 CustomClass：在每个1秒的时间段内，通过委托将消息发送到（A）视图控制器。

直到这里一切正常。一旦我返回到Main ViewController，委托就会保持活动状态，换句话说，委托更新A（ViewController）变量。我检查了（A）ViewController的viewDidDisappear被调用。当我再次从Main ViewController返回到（A）ViewController时，会创建一个新的变量实例。无论如何，我不明白这一点。

除了这个疑问之外，我想了解当我返回主视图控制器时代表保持活着的原因。我正在使用UINavigationItem进行导航。

我是IOS开发的初学者。

谢谢高级!!!

编辑1： （A）ViewController由Segue从MainViewController调用。 segue是通过故事板添加的。

MainViewController.swift

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

AViewController.swift

class ScanDevices : UIViewController, CustomClassDelegate {

    var myInts : [Int] = []

    var customClass : CustomClass!

    override func viewDidLoad() {
        super.viewDidLoad()

        print("viewDidLoad")

        if customClass == nil {
            customClass = CustomClass()
            customClass.customClassDelegate = self
        }
    }

    override func viewWillAppear(animated: Bool) {
        print("viewWillAppear")
    }

    override func viewDidAppear(animated: Bool) {
        print("viewDidAppear")
    }

    override func viewWillDisappear(animated: Bool) {
        print("viewWillDisappear")
    }

    override func viewDidDisappear(animated: Bool) {
        print("viewDidDisappear")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func didDiscoverPeripheralInt(peripheral: Int) {

        myInts.append(peripheral)
        print("Number = \(myInts.count)")
    }  
}

CustomClass.swift

class CustomClass : NSObject {

    var customClassDelegate : CustomClassDelegate?

    // MARK: init

    override init() {
        super.init()

        NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: "writeInt", userInfo: nil, repeats: true)
    }

    func writeInt () {
        CustomClassDelegate?.didDiscoverPeripheralInt(3)
    }
}

Answer 1

  var customClassDelegate : CustomClassDelegate?

您持有对您的委托的字符串引用。它必须是

 weak  var customClassDelegate : CustomClassDelegate?

看看以下文件： http://krakendev.io/blog/weak-and-unowned-references-in-swift

Answer 2

您的CustomClass拥有对该代表的强烈引用。您必须使用weak标记该属性：

weak var customClassDelegate : CustomClassDelegate?

看看为什么委托保持活着

2 个答案: