It returns nil by feature of Objective-C.
Referencing the class will translate into a runtime class lookup which will
return nil. Sending a message to nil will return nil.
The only caveat is that a class with that name could be provided by a library
and invalidate your code. But I would say improbable, and I would count on it.
Just be careful to never dereference those nils!
--
__Pascal Bourguignon__
> Le 10 sept. 2016 à 13:39, Andreas Falkenhahn <andr...@falkenhahn.com> a écrit
> :
>
> I want my app to run on 10.6 but use 10.7 features where available. Thus I'm
> compiling on 10.11 using -mmacosx-version-min=10.6. In particular, I want to
> use AVFoundation to play videos on 10.7 and better.
>
> To open a video, I do the following:
>
> AVPlayer *p = [[AVPlayer alloc] initWithURL:url];
>
> I'd expect this code to crash on 10.6 because 10.6 doesn't have AVPlayer.
> To my surprise, however, the code doesn't crash and it just returns NULL.
> This is fine because then my app will just show a message box informing
> the user that the file couldn't be opened and no other AVFoundation APIs
> will be accessed.
>
> However, I'm wondering whether it is ok to execute this code on 10.6 without
> any safeguard. I thought I'd have to do something like this instead:
>
> if(floor(NSAppKitVersionNumber) >= NSAppKitVersionNumber10_7) {
>
> AVPlayer *p = [[AVPlayer alloc] initWithURL:url];
> ...
>
> } else {
>
> return NULL;
> }
>
> Do I have to do this or can I just rely on alloc/init returning NULL for
> classes unknown on 10.6?
>
> --
> Best regards,
> Andreas Falkenhahn mailto:andr...@falkenhahn.com
>
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