@obj 协议委托方法在第二个 class 中不起作用。 Swift

Question

我试图在另一个 class 中调用协议委托。第一个 class (ViewController) 有效，但我实现它的第二个不显示任何数据。我用自动填充选项添加了它，所以它不会出错。它只是什么都不做。

发件人class

@objc protocol BWWalkthroughViewControllerDelegate{

  @objc optional func walkthroughPageDidChange(pageNumber:Int)     // Called when current page changes

}

@objc class BWWalkthroughViewController: UIViewController, UIScrollViewDelegate, ViewControllerDelegate {

  // MARK: - Public properties -

  weak var delegate:BWWalkthroughViewControllerDelegate?


  var currentPage:Int{    // The index of the current page (readonly)
    get{
      let page = Int((scrollview.contentOffset.x / view.bounds.size.width))
      return page
    }
  }


  // MARK: - Private properties -

  let scrollview:UIScrollView!
  var controllers:[UIViewController]!
  var lastViewConstraint:NSArray?
  var shouldCancelTimer = false
  var aSound: AVAudioPlayer!
  var isForSound: AVAudioPlayer!
  var alligatorSound: AVAudioPlayer!
  var audioPlayer = AVAudioPlayer?()
  var error : NSError?
  var soundTrack2 = AVAudioPlayer?()
  let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
  var audioPlayerAnimalSound = AVAudioPlayer?()
  var audioPlayerAlphabetSound = AVAudioPlayer?()
  var audioPlayerFullPhraze = AVAudioPlayer?()
  var audioPlayerPhonics = AVAudioPlayer?()

代码删除以保存 space 继续：

  /**
  Update the UI to reflect the current walkthrough situation
  **/

  private func updateUI(){

    // Get the current page

    pageControl?.currentPage = currentPage


    // Notify delegate about the new page

    delegate?.walkthroughPageDidChange?(currentPage)

  }

接收者class

class BWWalkthroughPageViewController: UIViewController, BWWalkthroughPage, ViewControllerDelegate, BWWalkthroughViewControllerDelegate {

第二个函数 Class。

func walkthroughPageDidChange(pageNumber: Int) {
    println("current page 2 \(pageNumber)")

  }

walkthroughPageDidChange 确实在 viewController class 中起作用。你能帮我看看哪里出了问题吗？

Answer 1

你的 weak var delegate:BWWalkthroughViewControllerDelegate? 是一个可选变量，它没有在你提供的代码中的任何地方赋值，因此它将是 nil。你必须在某个地方实例化它才能工作。

这样做的一个好方法是：

class BWWalkthroughViewController {
    let bwWalkthroughPageViewController = BWWalkthroughPageViewController()
    var bwWalkthroughViewControllerDelegate : BWWalkthroughViewControllerDelegate!

    init() {
        bwWalkthroughViewControllerDelegate = bwWalkthroughPageViewController as BWWalkthroughViewControllerDelegate
    }
}

需要注意的一点是，用有意义的名称命名委托通常是一种很好的做法。关键字 "delegate" 经常用于许多类并且受到限制。更详细的名称将消除覆盖原始委托的机会，并且如果您有多个委托，将有助于识别每个委托。

@obj 协议委托方法在第二个 class 中不起作用。 Swift

@obj protocol delegate method not working in second class. Swift

delegates

protocols

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