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:

1. Owner should catch events from its view. I.e. TaskUIViewController sould be a target to UIPanGestureRecognizer which you added to its view.
2. If a controller has a sub-controller and waits from its sub-controller some responses – implement this as delegate.
3. 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