Question

I’ve subclassed a UILabel and added 2 properties that look like this:

@property (nonatomic, assign) SEL action;
@property (nonatomic, assign) id target;

I then implemented UIView’s touches began method like this:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{

    if ([target respondsToSelector:@selector(action)]) {
        [target performSelector:@selector(action) onThread:[NSThread mainThread] withObject:nil waitUntilDone:NO];
    }
}

within the class containing the subclassed UILabel, i set the target and action like this:

    label.target = self;
    labek.action = @selector(myMethod);
    label.userInteractionEnabled = YES;

The class including the label does indeed have the method myMethod, and so it should respond to it. Any ideas why it might not?

thanks!

Answer 1

You are setting your action like this label.action = @selector(myMethod); and then using action and passing it into a second selector [target respondsToSelector:@selector(action)]. That will not work.

You want to do this:

if ([target respondsToSelector:self.action]) {
    [target performSelector:self.action onThread:[NSThread mainThread] withObject:nil waitUntilDone:NO];
}

Basically, the if statement fails because the target does not respond to that selector. Therefore, it is never being called.