Question

I created class ChImage from UIImage

@interface ChImage : UIImage {
@public
    int ChannelId;
    NSString *ChannelName;
    NSString *Description;

}

@property(nonatomic, retain) NSString *ChannelName;
@property(nonatomic, retain) NSString *Description;

@end

@implementation ChImage


@synthesize ChannelName;
@synthesize Description;

@end

And use it in the code:

ChImage *cho = [ChImage imageNamed:img];
        cho = [ChImage imageNamed:img];
        cho.ChannelName = @"something here...";

on the line cho.ChannelName application breaks. I need to extend UIImage because I need some extra property in that class but I don’t know what am I doing wrong?

Also when I try to get image from UIImageView I got error. I don’t know if this have something with upper problem:

UIImageView *iw = (UIImageView*) sender;
    ChImage *im = (ChImage*) iw.image;

I just try to cast in another part of code and it works. The problem must be in click handling method. This is that method:

- (void)imageTapped:(UIGestureRecognizer *)sender
{
    UIImageView *iw = (UIImageView*) sender;
    ChImage *im = (ChImage*) iw.image;
    NSLog(im.ChannelName);

}

Becouse this is a uiscrollview with images inside this is how i attached click event to every image:

for (imageToAdd in arrayOfImages)
    {               
        UIImageView *temp = [[UIImageView alloc] initWithImage:imageToAdd];     

        temp.frame = CGRectMake(x, y, 29, 29);
        temp.userInteractionEnabled = YES;      
        x += 29;        

        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageTapped:)];
        [temp addGestureRecognizer:tap];    

        [scrollView addSubview:temp];

    }

Answer 1

It is not recommend to subclass UIImage, it is a OO layer on top of CGImageRef and have quite allot of magic involved.

You could create a wrapper class, and do a has-a relationship instead of a is-a relationship. Which seems like a much better approach in your case.

• Not: Channel is-a Image.
• Instead: Channel has-a Image.

Like this:

@interface Channel : NSObject {
@private
   NSString* _name;
   NSString* _description;
   UIImage* _image; 
}
// The rest…

You should probably change the name description since it will conflict with -[NSObject description].