Question

Currently I have in my code

tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(addCompoundToLabel:)];

My code would be cleaner if it was something like

tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(addCompoundToLabel:) withObject:data];

I read that associated objects allow you to pass objects in a gesture recognizer, but after reading the docs, I don’t quite understand how to implement it into my code. An example implementation of associated objects would be appreciated. Thanks

EDIT:

this is what the beginning of addCompound looks like

- (void)addCompoundToLabel:(UIGestureRecognizer *)recognizer {

 if( [recognizer state] == UIGestureRecognizerStateEnded ) {

      FormulaLabel* label = (FormulaLabel*)[recognizer view];  

Answer 1

Using associated objects is a messy solution. Instead, you could create a false target object, give it your UIView and your Data, and have access to both of them in the selector method. It is a lot more readable, and your code expresses your intent a lot better.

Here is a quick and dirty example:

@interface FalseTarget : NSObject {
    MyViewController *_viewCtrl;
    MyData *_data;
}
-(id)initWithViewCtrl:(MyViewController*)viewCtrl andData:(MyData*)data;
-(void)tap:(id)sender;
@end

@implementation
-(id)initWithViewCtrl:(MyViewController*)viewCtrl andData:(MyData*)data {
    self = [super init];
    if (self) {
        _viewCtrl = viewCtrl;
        _data = data;
    }
    return self;
}
-(void)tap:(id)sender {
    [_viewCtrl processTapFromSender:sender withData:_data];
}
@end

Add processTapFromSender:withData: method to your controller:

-(void)processTapFromSender:(id)sender withData:(MyData*)data {
    // Your action
}

Now you can create your tap recognizer like this:

FalseTarget *target = [[FalseTarget alloc] initWithViewCtrl:self andData:data];
tap = [[UITapGestureRecognizer alloc] initWithTarget:target action:@selector(tap:)];