Question

Using the GestureRecognizer attached to a view triggers my app to crash with EXC_BAD_ACCESS error. Here’s the classes involved

• BoardViewController – Displaying a board (as background) set as rootViewController in the AppDelegate. It instantiates multiple objects of the “TaskViewcontroller”.

//BoardViewController.h
@interface BoardViewController : UIViewController {
    NSMutableArray* allTaskViews; //for storing taskViews to avoid having them autoreleased
}

 

//BoardViewController.m - Rootviewcontroller, instantiating TaskViews    
- (void)viewDidLoad
{
    [super viewDidLoad];
    TaskViewController* taskA = [[TaskViewController alloc]init];
    [allTaskViews addObject:taskA];
    [[self view]addSubview:[taskA view]];
}

• TaskViewController – An indivual box displayed on the board. It should be draggable. Therefore I attached UIPanGestureRecoginzer to its view

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIPanGestureRecognizer* panRecognizer = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePan:)];
    [[self view] addGestureRecognizer:panRecognizer];
}

- (void)handlePan:(UIPanGestureRecognizer *)recognizer {
    NSLog(@"PAN!");
}

The .xib file is a simple view.

All programming with the gesture recognizer I’d prefer to do in code. Any idea how to fix the error causing the app crash?

Answer 1

The method handlePan is on your view controller, not on your view. You should set the target to self:

UIPanGestureRecognizer* panRecognizer = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePan:)];

EDIT (in response to the edit of the question) As omz has correctly noted, your TaskViewController gets released upon BoardViewController‘s viewDidLoad: exit. There are two ways of dealing with it:

• Fold the handlePan method into the parent view controller, along with the code of viewDidLoad:, or
• Make an instance variable for TaskViewController *taskA, rather than making it a local variable.