Nice shortcuts for creating and accessing ObjC Associated Values.

AssociatedValues+AtoZ.m

@implementation NSObject (AtoZ_AssociatedValues)

- (void) setAssociatedValue: (id)value  forKey: (NSString*) key {  
    
    [self setAssociatedValue:value forKey:key policy:OBJC_ASSOCIATION_ASSIGN]; 
}

- (void) setAssociatedValue: (id)value  forKey: (NSString*) key  policy: (objc_AssociationPolicy) policy {	

    objc_setAssociatedObject(self, (__bridge const void *)(key), value, policy); 
}

- (id) associatedValueForKey: (NSString*) key {	

     return objc_getAssociatedObject(self, (__bridge const void *)(key)); 
}

- (void) removeAssociatedValueForKey: (NSString*) key { 	

    objc_setAssociatedObject(self, (__bridge const void *)(key), nil, OBJC_ASSOCIATION_ASSIGN); 
}

- (void)removeAllAssociatedValues { 	objc_removeAssociatedObjects(self); }

- (BOOL) hasAssociatedValueForKey:(NSString*)string {  

    return [self associatedValueForKey:string] != nil; 
}

- (id) associatedValueForKey:(NSString*)key orSetTo:(id)anObject policy: (objc_AssociationPolicy) policy {
	return 	[self hasAssociatedValueForKey:key]
	? 	[self associatedValueForKey:   key]
		: ^{	[self setAssociatedValue:anObject forKey:key policy:policy];
			return [self associatedValueForKey:key];
		}();
}

@end