Adding Properties to an Objective-C Category – Revisted

http://www.davidhamrick.com/2012/05/28/Adding-Properties-to-an-Objective-C-Category-Revisted.html

In my last post I wrote about adding properties to a category in objective-c. I have ended up using this feature quite a bit recently so I wrote a macro that will add the appropriate methods.

Before, when I wanted to add a category I would have to manually add the setter and getter.

static char kDHStyleKey;
@interface UIView (DHStyleManager)
@property (nonatomic, copy) NSString* styleName;
@end
@implementation UIView (DHStyleManager)
@dynamic styleName;
- (void)setStyleName:(NSString *)styleName
{
objc_setAssociatedObject(self, &kDHStyleKey, styleName, OBJC_ASSOCIATION_COPY);
}
- (NSString*)styleName
{
return objc_getAssociatedObject(self, &kDHStyleKey);
}
@end

Now, all I need to do is use the macro to create the getters and setters.

@interface UIView (DHStyleManager)
@property (nonatomic, copy) NSString* styleName;
@end
@implementation UIView (DHStyleManager)
ADD_DYNAMIC_PROPERTY(NSString*,styleName,setStyleName);
@end

All you need to do to use this macro is put this in a header file.

#define ADD_DYNAMIC_PROPERTY(PROPERTY_TYPE,PROPERTY_NAME,SETTER_NAME) \
@dynamic PROPERTY_NAME ; \
static char kProperty##PROPERTY_NAME; \
- ( PROPERTY_TYPE ) PROPERTY_NAME \
{ \
return ( PROPERTY_TYPE ) objc_getAssociatedObject(self, &(kProperty##PROPERTY_NAME ) ); \
} \
\
- (void) SETTER_NAME :( PROPERTY_TYPE ) PROPERTY_NAME \
{ \
objc_setAssociatedObject(self, &kProperty##PROPERTY_NAME , PROPERTY_NAME , OBJC_ASSOCIATION_RETAIN); \
} \