NSMutableDIctionary setObject: ForKey crashing when Key is member of Object - objective-c

Question

I'm trying to use an NSMutableDictionary to pair my custom classes object with a UIButton as it's key. The UIButton that is the key is also a member of the object that I want to store as the object in the NSMutableDictionary.
My Class definition looks like ths:
#interface ClassA : NSObject {
#public
UIButton *button1;
UIButton *button2;
UILabel *label;
}
#property (nonatomic, retain) UIButton *button1;
#property (nonatomic, retain) UIButton *button2;
#property (nonatomic, retain) UILabel *label;
#end
And my implementation is just this:
#implementation ClassA
#synthesize button1, button2, label;
#end
The NSMutableDictionary is in another class. I define it in the implementation like this:
#interface UIClass1 : UIViewController {
NSMutableDictionary *Dictionary;
}
-(void)DoWork;
#property (nonatomic, retain) NSMutableDictionary *Dictionary;
#end
And the part where I'm trying to set the Dictionary values is done here:
-(void)DoWork{
Dictionary = [[NSMutableDictionary alloc] init];
ObjectA = [[ClassA alloc] init];
ObjectA->button1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
ObjectA->button2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
ObjectA->label = [[[UILabel alloc] initWithFrame:CGRectMake(20, 20, 20, 20)] autorelease]
/* THIS IS A TEST AND IT WORKS FINE */
NSString *str = [[NSString alloc] initWithFormat:#"test"];
[Dictionary setObject:obj1 forKey:str];
/*THIS IS WHAT I WOULD ACTUALLY LIKE TO DO */
[Dictionary setObject:Object1 forKey:ObjectA->button1];
[Dictionary setObject:ObjectA forKey:ObjectA->button2];
}
I've followed this code through my debugger and when I get to this line:
[Dictionary setObject:Object1 forKey:ObjectA->button1];
It just crashes SIGABRT. None of my variables are nil, every object has been allocated.
Any ideas as to why I can't set the key to the button from ClassA but I can set it the the NSString I created as a test?

Answer 1

The object you use as a key in an NSMutableDictionary must conform to the NSCopying protocol.
From Apple docs:
The key for value. The key is copied (using copyWithZone:; keys must
conform to the NSCopying protocol). The key must not be nil.
UIButton does not conform to NSCopying.

Answer 2

Try using
forKey:[NSValue valueWithPointer:ObjectA->button1]