Re: minor ARC casting question
Re: minor ARC casting question
- Subject: Re: minor ARC casting question
- From: Igor Mozolevsky <email@hidden>
- Date: Sun, 30 Oct 2011 15:55:39 +0000
On 30 October 2011 15:15, Matt Neuburg <email@hidden> wrote:
> In ARC, this is legal:
>
> self.view.layer.contents = (id)[[UIImage imageNamed:@"boat.gif"] CGImage];
>
> And this is legal:
>
> id ref = (id)[[UIImage imageNamed:@"boat.gif"] CGImage];
> self.view.layer.contents = ref;
>
> But this is not:
>
> CGImageRef ref = [[UIImage imageNamed:@"boat.gif"] CGImage];
> self.view.layer.contents = (id)ref; // compilation fails
>
> In the last case, I have to change id to __bridge id. My question is: What's the difference in the cases? In all situations I'm casting a CGImageRef to an id, so why does ARC permit this in the first cases but not in the last? Is it because UIImage's CGImage method is a method, and this fact somehow gives ARC further info? Thx - m.
The compiler knows how to handle CF objects returned from Cocoa
methods, but doesn't know how to handle stuff created by yourself. I
thought that was fairly obvious from and explicit in the Transitioning
Notes?
Cheers,
--
Igor ;-)
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