Swift如何取得View所属的ViewController

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从VC取得View很容易,但有些情况下我们需要从View反向获取VC.

不过在一些特殊的场合,Cocoa库帮我们想的很周到,比如在自定义View过渡动画的时候:

func animateTransition(transitionContext: UIViewControllerContextTransitioning) {}

系统在回调我们的animateTransition方法时,会传入一个context参数,从它我们可以轻松取得参与动画的toView,fromView以及它们对应的VC:

let toView = transitionContext.viewForKey(UITransitionContextToViewKey)!let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)!let fromView = transitionContext.viewForKey(UITransitionContextFromViewKey)!let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)!

但不是所有情况系统都会帮你考虑的这么周到,所以有时候还得需要自己从View找到它的VC,网上有Obj-c的代码示例:

- (UIViewController *)viewController {    for (UIView* next = [self superview]; next; next = next.superview) {        UIResponder *nextResponder = [next nextResponder];        if ([nextResponder isKindOfClass:[UIViewController class]]) {            return (UIViewController *)nextResponder;        }    }    return nil;}

我们来将其改为Swift版本,以下是第一次尝试:

func controller(view:UIView)->UIViewController?{        for var next:UIView? = view;next != nil;next = next!.superview{            if let nextResponder = next?.nextResponder() where nextResponder.isKindOfClass(UIViewController.self){                return (nextResponder as! UIViewController)            }        }        return nil    }

上面的方法可以很好的完成其功能,不过编译器有警告,for如此的语法将会在将来的Swift版本中剔除,所以我们还是将其转成没有警告的代码:

func controller2(view:UIView)->UIViewController?{        var next:UIView? = view        repeat{            if let nextResponder = next?.nextResponder() where nextResponder.isKindOfClass(UIViewController.self){                return (nextResponder as! UIViewController)            }            next = next?.superview        }while next != nil        return nil    }

正如你所见,虽然没有警告,但是代码要稍微多一些了.

最后我们可以把开始的代码替换如下:

let toView = transitionContext.viewForKey(UITransitionContextToViewKey)!let fromView = transitionContext.viewForKey(UITransitionContextFromViewKey)!let toVC = controller2(toView)!let fromVC = controller2(fromView)!

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