gistfile1.txt

// Public 
@interface Image()

@property (assign, nonatomic, readonly) CGSize size;

@end



// Private 
@interface Image()

@property (assign, nonatomic, readwrite) CGSize size;

@property (assign, nonatomic, readonly) CGFloat width;
@property (assign, nonatomic, readonly) CGFloat height;

@end



@implementation Image ()


- (void)mantleDidFinishParsing
{
    _size = CGSizeMake (self.width, self.height);
}

@end