Question

Possible Duplicate:
Subclass UIButton to add a property

I’m trying to find a way to extend UIButton so that it can have a property like

@property(assign, nonatomic) id userInfos;

without subclassing it…

Is this possible?

the button.tag is not enough in my situation…

Okay as always a better answer is available here

Subclass UIButton to add a property

Answer 1

This is very easy using Objective-C associated objects:

In your header:

@interface UIButton (MyCustomProperty)
@property (readwrite, retain, nonatomic) id myCustomProperty;
@end

In your implementation file:

#include <objc/runtime.h>

/* Associated objects need a unique memory location to use as a key. */
static char MyCustomPropertyKey = 0;

@implementation UIButton (MyCustomProperty)
/* Use @dynamic to tell the compiler you're handling the accessors yourself. */
@dynamic myCustomProperty;

- (id)myCustomProperty {
    return objc_getAssociatedObject(self, &MyCustomPropertyKey);
}

- (void)setMyCustomProperty: (id)anObject {
    objc_setAssociatedObject(self, &MyCustomPropertyKey, anObject, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
@end

That’s it!