如何在Swift中将（可选）完成处理函数闭包传递给transitionFromViewController？

Question

在我的应用程序的ViewController中，我调用了transitionFromViewController，但在将闭包传递给completion：参数时总是得到以下错误。

Type '() -> Void' does not conform to protocol 'NilLiteralConvertible' 

这里的函数调用：

self.transitionFromViewController(
     self.currentVC, 
     toViewController: newController, 
     duration: 0.2, 
     options: UIViewAnimationOptions.TransitionCrossDissolve, 
     nil, 
     completion: { finished in 
      fromViewController.removeFromParentViewController() 
      toViewController.didMoveToParentViewController(containerViewController) 
      toViewController.view.frame = containerViewController.view.bounds 
    }) 

根据代码完成方法签名如下：

transitionFromViewController(fromViewController: UIViewController, toViewController: UIViewController, duration: NSTimeInterval, options: UIViewAnimationOptions, animations:() -> Void(), completion: ((Bool) -> Void)?) 

Answer 1

你不能传递零至animations宣布为不optional

抱器 () -> Void()

传递空closure如果你想

self.transitionFromViewController(
     self.currentVC, 
     toViewController: newController, 
     duration: 0.2, 
     options: UIViewAnimationOptions.TransitionCrossDissolve, 
     animations: {() -> Void in 

     }, 
     completion: { finished in 
      fromViewController.removeFromParentViewController() 
      toViewController.didMoveToParentViewController(containerViewController) 
      toViewController.view.frame = containerViewController.view.bounds 
    }) 

Answer 2

我想下面的代码应该帮助你：哪里，//用于动画代码

self.transitionFromViewController(fromViewController, toViewController: toViewController, duration: 0.1, options: UIViewAnimationOptions.CurveEaseInOut, animations: {() -> Void in 
      // code for animations 
      }) { (value: Bool) -> Void in 
      // code after completion 
     } 

- 代码你想要的块期间执行。 而且，//完成之后的代码 - 您要在块完成之后执行的代码。