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 {
@H_403_36@for (UIView* @H_403_36@next = [@H_403_36@self superview]; @H_403_36@next; @H_403_36@next = @H_403_36@next.superview) {
UIResponder *nextResponder = [@H_403_36@next nextResponder];
@H_403_36@if ([nextResponder isKindOfClass:[UIViewController @H_403_36@class]]) {
@H_403_36@return (UIViewController *)nextResponder;
}
}
@H_403_36@return @H_403_36@nil;
}
我们来将其改为Swift版本,以下是第一次尝试:
func controller(view:UIView)->UIViewController?{
@H_403_36@for var next:UIView? = view;@H_403_36@next != @H_403_36@nil;@H_403_36@next = @H_403_36@next!.superview{
@H_403_36@if let nextResponder = @H_403_36@next?.nextResponder() where nextResponder.isKindOfClass(UIViewController.@H_403_36@self){
@H_403_36@return (nextResponder as! UIViewController)
}
}
@H_403_36@return @H_403_36@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
@H_403_36@repeat{
@H_403_36@if let nextResponder = next?.nextResponder() where nextResponder.isKindOfClass(UIViewController.self){
@H_403_36@return (nextResponder as! UIViewController)
}
next = next?.superview
}@H_403_36@while next != @H_403_36@nil
@H_403_36@return @H_403_36@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)!