Setting the contents of a CALayer to a CGImageRef on iOS with ARC on

Question

The following code compiles fine with manual memory management, but fails under ARC:

CALayer *layer = [CALayer layer];
layer.contents = [[UIImage imageNamed:@"dial.png"] CGImage];

The error is:

Automatic Reference Counting Issue: Implicit conversion of a non-Objective-C pointer type 'CGImageRef' (aka 'struct CGImage *') to 'id' is disallowed with ARC

How can I get this running with ARC?

Answer 1

CoreFoundation objets aren't managed by ARC. ARC only works with Objective-C objets and does not implicitly know how to transfer the ownership when casting from (or to) an non-object pointer type.

You need to tell ARC how the ownership of the objet is transferred during the cast:

layer.contents = (__bridge id) [[UIImage imageNamed:@"dial.png"] CGImage];