How to add associated object to uitapgesture? - objective-c

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:)];