iphone - Making deep copy of UIImage

Question

My class contains an UIImage property which I want to enforce as a 'copy' property by any external clients accessing it. But, when I try to do a copy in my custom setter, I get the runtime error about UIImage not supporting copyWithZone. So what's a good way to ensure that the correct ownership policy is followed?

// declared in the interface as:
@property (nonatomic, readonly, copy) UIImage *personImage;

// class implementation
- (void)setPersonImage:(UIImage *)newImage
{
    if (newImage != personImage) 
    {
        [personImage release];

        // UIImage doesn't support copyWithZone
        personImage = [newImage copy];
    }
}

Answer 1

Here is a way to do it:

UIImage *imageToCopy = <# Your image here #>;
UIGraphicsBeginImageContext(imageToCopy.size);
[imageToCopy drawInRect:CGRectMake(0, 0, imageToCopy.size.width, imageToCopy.size.height)];
UIImage *copiedImage = [UIGraphicsGetImageFromCurrentImageContext() retain];
UIGraphicsEndImageContext();   

The reason I needed this is that I had an image variable initialized with imageWithContentsOfFile:, and I wanted to be able to delete the file from disk but keep the image variable. I was surprised to find that when the file is deleted the image variable goes crazy. It was displaying wacky random data even though it was initialized before the file was deleted. When I deep copy first it works fine.