UIGestureRecognizer - Get the reference to the touched UIViewController Instead of its View? - objective-c

Question

How do I get a reference to the UIViewController of a touched view?
I am using a UIPanGestureRecognizer on the view of a UIViewController. Here's how I initialize it:
TaskUIViewController *thisTaskController = [[TaskUIViewController alloc]init];
[[self view]addSubview:[thisTaskController view]];
UIPanGestureRecognizer *panRec = [[UIPanGestureRecognizer alloc]initWithTarget:self action:#selector(handlePan:)];
[[thisTaskController view] addGestureRecognizer:panRec];
In the tiggered action triggered using the gesture recognizer I am able to get the view from the parameter using recognizer.view
- (IBAction)handlePan:(UIPanGestureRecognizer *)recognizer {
UIView *touchedView = [[UIView alloc]init];
touchedView = (UIView*)[recognizer view];
...
}
However what I really need is the underlying UIViewController of the view touched. How can I get a reference to the UIViewController that contains this view instead of only the UIView?

Answer 1

I would say that it is more a design issue than just getting a reference. So I would follow several simple advises:
Owner should catch events from its view. I.e. TaskUIViewController sould be a target to UIPanGestureRecognizer which you added to its view.
If a controller has a sub-controller and waits from its sub-controller some responses - implement this as delegate.
You have memory leak in your "handlePan:" method.
Here is a skeleton to solve your issue:
#protocol CallbackFromMySubcontroller <NSObject>
- (void)calbackFromTaskUIViewControllerOnPanGesture:(UIViewController*)fromController;
#end
#interface OwnerController : UIViewController <CallbackFromMySubcontroller>
#end
#implementation OwnerController
- (id)init
{
...
TaskUIViewController *thisTaskController = [[TaskUIViewController alloc] init];
...
}
- (void)viewDidLoad
{
...
[self.view addSubview:thisTaskController.view];
...
}
- (void)calbackFromTaskUIViewControllerOnPanGesture:(UIViewController*)fromController
{
NSLog(#"Yahoo. I got an event from my subController's view");
}
#end
#interface TaskUIViewController : UIViewController {
id <CallbackFromMySubcontroller> delegate;
}
#end
#implementation TaskUIViewController
- (id)initWithOwner:(id<CallbackFromMySubcontroller>)owner
{
...
delegate = owner;
...
}
- (void)viewDidLoad
{
UIPanGestureRecognizer *panRec = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handlePan:)];
[self.view addGestureRecognizer:panRec];
[panRec release];
}
- (void)handlePan:(UIPanGestureRecognizer *)recognizer {
...
[delegate calbackFromTaskUIViewControllerOnPanGesture:self];
...
}
#end

Answer 2

[touchedView nextResponder] will return the UIViewController object that manages touchedView (if it has one) or touchedView's superview (if it doesn’t have a UIViewController object that manages it).
For more information, see the UIResponder Class Reference. (UIViewController and UIView are subclasses of UIResponder.)
In your case, since you happen to know that touchedView is your viewController's view (and not, for instance, a subview of your viewController's view), you can just use:
TaskUIViewController *touchedController = (TaskUIViewController *)[touchedView nextResponder];
In the more general case, you could work up the responder chain until you find an object of kind UIViewController:
id aNextResponder = [touchedView nextResponder];
while (aNextResponder != nil)
{
if ([aNextResponder isKindOfClass:[UIViewController class]])
{
// we have found the viewController that manages touchedView,
// so we break out of the while loop:
break;
}
else
{
// we have yet to find the managing viewController,
// so we examine the next responder in the responder chain
aNextResponder = [aNextResponder nextResponder];
}
}
// outside the while loop. at this point aNextResponder points to
// touchedView's managing viewController (or nil if it doesn't have one).
UIViewController *eureka = (UIViewController *)aNextResponder;