获取 uiview 的 uiviewcontroller

- (UIViewController *)viewController {
	/// Finds the view's view controller.
	// Traverse responder chain. Return first found view controller, which will be the view's view controller.
	UIResponder *responder = self;
	while ((responder = [responder nextResponder]))
		if ([responder isKindOfClass: [UIViewController class]])
			return (UIViewController *)responder;
	
	// If the view controller isn't found, return nil.
	return nil;
}

/// 返回所在的导航控制器
- (UINavigationController *)navigationController {
	UIResponder *responder = self;
	while ((responder = [responder nextResponder]))
		if ([responder isKindOfClass: [UINavigationController class]])
			return (UINavigationController *)responder;
	return nil;
}