获取UIView的视图控制器（Swift）

UIView继承自UIResponder，可以利用UIResponder的nextResponder()方法返回该视图的控制器，以下是官方文档对该方法的描述：

The UIResponder class does not store or set the next responder automatically, instead returningnil by default. Subclasses must override
this method to set the next responder.UIView implements this method by returning theUIViewController
object that manages it (if it has one) or its superview (if it doesn’t);UIViewController
implements the method by returning its view’s superview;UIWindow returns the application object, andUIApplication returns
nil.

因为我要经常用到该方法，所以我直接扩展到UIView里面去了：

extension UIView {
func parentViewController() -> UIViewController? {
for (var next = self.superview; next != nil; next = next?.superview) {
let ctr = next?.nextResponder()
if (ctr is UIViewController) {
return ctr as? UIViewController
}
}
return nil
}
}