我有一些与 UI 相关的功能，例如显示警告弹出窗口、在屏幕中间显示事件指示器，或者在屏幕上显示带有自定义消息的动画 UIView。
我想在多个 viewControllers 中使用 ( VC1，在本例中为 VC2)，所以我不再重复。
最初，我有以下代码，适用于从负责这些功能的 BaseVC 继承的两个 VC。
VC1​​是内嵌tablelView的UIViewController，VC2是内嵌collectionView的UIViewController。

class VC1: BaseVC {
    func viewDidAppear(animated: Bool) {
        activityIndicatorBegin()
    }

    func btnPressed() {
        activityIndicatorEnd()
    }
}

class VC2: BaseVC {
    func viewDidAppear(animated: Bool) {
        activityIndicatorBegin()
    }

    func btnPressed() {
        activityIndicatorEnd()
    }
}

class BaseVC: UIViewController {

    var activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView()
    var isCustomViewOnScreen = false

    func activityIndicatorBegin() {
        if activityIndicator.isAnimating() == false {
            activityIndicator = UIActivityIndicatorView(frame: CGRectMake(0,0,20,20))
            activityIndicator.center = view.center
            activityIndicator.hidesWhenStopped = true
            activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.WhiteLarge
            activityIndicator.color = UIColor.blackColor()
            view.addSubview(activityIndicator)
            activityIndicator.startAnimating()
        }
    }

    func activityIndicatorEnd() {
        if activityIndicator.isAnimating() == true {
            activityIndicator.stopAnimating()
            activityIndicator.removeFromSuperview()
        }
    }

    func animateACustomViewOnScreen() {
        if isCustomViewOnScreen == false {
            // Some animation code 
        }
    }

    func removeCustomView() {
        if isCustomViewOnScreen == true {
            // Some removal code
        }
    }
}

但是，由于某些原因，我决定让 VC1 直接用于 UITableViewController，而 VC2 来自 UICollectionViewController。
这意味着他们不再可以从 UIViewController 类的 BaseVC 中调用。
< br/="">如何才能让两个VC都能达到那些功能？

最佳答案

答案是Protocol Extensions .您将 BaseVC 定义为协议(protocol)，然后通过添加将在实现它的整个类中使用的共享逻辑来扩展它:

(在下面的示例中，BaseVC 重命名为 ActivityIndi​​catorDisplaying。)

protocol ActivityIndicatorDisplaying {

  var activityIndicator: UIActivityIndicatorView { get set }
  var showsCustomView: Bool { get }

  func showActivityIndicator()
  func dismissActivityIndicator()
}

extension ActivityIndicatorDisplaying where Self: UIViewController {

  func showActivityIndicator() {
    if activityIndicator.isAnimating() { return }

    activityIndicator.center = CGPointMake(view.bounds.width / 2, view.bounds.height / 2)
    activityIndicator.hidesWhenStopped = true
    activityIndicator.activityIndicatorViewStyle = .WhiteLarge
    activityIndicator.color = UIColor.blackColor()
    view.addSubview(activityIndicator)
    activityIndicator.startAnimating()
  }

  func dismissActivityIndicator() {
    activityIndicator.stopAnimating()
    activityIndicator.removeFromSuperview()
  }

  func animateACustomViewOnScreen() {
    if !showsCustomView {
      // Some animation code
    }
  }

  func removeCustomView() {
    if showsCustomView {
      // Some removal code
    }
  }
}

class VC1: UITableViewController, ActivityIndicatorDisplaying {

  var activityIndicator = UIActivityIndicatorView()
  var showsCustomView: Bool = false

  override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)

    showActivityIndicator()
  }

  func btnPressed() {
    dismissActivityIndicator()
  }
}

class VC2: UICollectionViewController, ActivityIndicatorDisplaying {

  var activityIndicator = UIActivityIndicatorView()
  var showsCustomView: Bool = true

  ...
}

关于ios - View Controller 之间的共享 UI 功能，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/39782526/