8

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?

cfischer
  • 24,452
  • 37
  • 131
  • 214
  • 1
    I haven't used ARC but have you tried making it an *explicit* conversion, casting it to `(id)`? – progrmr Dec 20 '11 at 15:39

2 Answers2

18

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];
Nicolas Bachschmidt
  • 6,475
  • 2
  • 26
  • 36
1

Just cast the result of -CGImage to a id, as it is complaining about implicit conversions...

layer.contents = (id) [[UIImage imageNamed:@"dial.png"] CGImage];
Richard J. Ross III
  • 55,009
  • 24
  • 135
  • 201
  • 1
    Hhmm, the compiler did stop bitching, but any idea why this is a no-no with ARC? – cfischer Dec 20 '11 at 15:46
  • 2
    Because a `id` represents a `struct objc_object *`, where a `CGImageRef` represents a `struct CGImage *` (which is a `struct objc_object *` under the covers), which isn't a `struct objc_object *` the compiler cannot implicitly convert a non-object (especially one that is retained in the property) to an object. – Richard J. Ross III Dec 20 '11 at 15:48