Adding a property to all of my UIControls

Im trying to make it so that every single UIControl in my application (UIButton, UISlider, etc) all have special extra properties that I add to them.

I tried to accomplish this by creating a UIControl Category and importing it where needed but I have issues.

Here is my code.

My setSpecialproperty method gets called but it seems to be getting called in an infinite loop until the app crashes.

Can you tell me what Im doing wrong or suggest a smarter way to add a property to all of my UIControls?

@interface UIControl (MyControl)
{

}
@property(nonatomic,strong) MySpecialProperty  *specialproperty;

-(void)setSpecialproperty:(MySpecialProperty*)param;
@end

////////

#import "UIControl+MyControl.h"

@implementation UIControl (MyControl)

-(void)setSpecialproperty:(MySpecialProperty*)param
{
    self.specialproperty=param;
}

///////////////

#import "UIControl+MyControl.h"

@implementation ViewController


UIButton *abutton=[UIButton buttonWithType:UIButtonTypeCustom];
MySpecialProperty *prop=[MySpecialProperty alloc]init];
[abutton setSpecialproperty:prop];

Solution

While you can't add an iVar to UIControl via a category, you can add Associated Objects, which can be used to perform much the same function.

So, create a category on UIControl like this:

static char kControlNameKey;

- (void) setControlName: (NSString *) name
{
    objc_setAssociatedObject(self, &kControlNameKey, name, OBJC_ASSOCIATION_COPY);
}

- (NSString *) controlName
{
    return (NSString *)objc_getAssociatedObject(array, &kControlNameKey);
}

There's more to it than that, I guess you'll need to check if an association exists before setting a new one, otherwise it will leak, but this should give you a start.

See the Apple Docs for more details