iphone - Releasing CGImage (CGImageRef)

Question

I'm curious if I'm following proper memory management with CGImageRef, which I'm passing through several methods (since it's CG object, I assume it doesn't support autorelease). Memory management with non-NSObjects and interaction with other NSObjects is still somewhat new to me.

Here what I'm doing:

I'm creating the CGImageRef inside my image cache manager with CGBitmapContextCreateImage (retain count 1), and adding it to the NSMutableDictionary (retain count 2).

When CALayers use the image, I assign with layer.contents (retain count +1), and clearing contents with layer.contents = nil (retain count -1) before removing the layer.

Finally, when clearing the texture, I call CGImageRefRelease and [NSMutableDictionary removeObject] to have retain count as 0.

Is this a proper way to do so?

Answer 1

Core Foundation objects (which all Core Graphics objects are) do support autorelease.

The steps you describe should work just fine and not leak or over-release the object.

I use CFRelease instead of specific-class release functions like CGImageRelease, but purely as a matter of style. I just have to beware of NULL: CGImageRelease checks for NULL, whereas CFRelease will crash when passed NULL. Using CGImageRelease and its siblings means you don't have to worry about this.

I'm assuming you meant removeObject:forKey:, not removeObject (which doesn't exist and wouldn't have somewhere to specify an object anyway).