ios - @obj 协议(protocol)委托(delegate)方法在第二类中不起作用。 swift

Question

我正在尝试在另一个类中调用协议(protocol)委托(delegate)。第一个类(ViewController)有效，但我实现的第二个类不显示任何数据。我使用自动填充选项添加了它，因此它不会给出错误。它只是没有做任何事情。

发送者类别

@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?()

删除代码以节省空间继续:

  /**
  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)

  } 

接收者类别

class BWWalkthroughPageViewController: UIViewController, BWWalkthroughPage, ViewControllerDelegate, BWWalkthroughViewControllerDelegate {

第二类函数。

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

  }

然而，walkthroughPageDidChange 在 vi​​ewController 类中确实有效。请您帮我看看哪里出了问题？

Answer 1

您的 weak var delegate:BWWalkthroughViewControllerDelegate? 是一个可选变量，它没有在您提供的代码中的任何位置分配，因此它将为零。您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
    }
}

需要注意的是，使用有意义的名称来命名委托(delegate)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(delegate)的机会，并且如果您有多个委托(delegate)，将有助于识别每个委托(delegate)。