> On Sep 10, 2016, at 5:16 AM, Pascal Bourguignon <[email protected]>
> wrote:
>
> 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.
Well, not exactly. If you reference the class name as a literal, as in
[AVPlayer alloc], that does result in a link-time reference to a symbol
.objc_class_name_AVPlayer. If that class doesn’t exist when the app is being
loaded, it will fail to launch with a fatal dyld error.
Things would work as you describe if the class were being looked up by name,
like
[[NSClassFromString(@“AVPlayer”) alloc] init]
since NSClassFromString would return Nil.
Andreas, I think the reason your code doesn’t crash is that the linker is
importing AVFoundation as a weak library (probably because of the minimum OS
version you declared at build time.) That means that if the library doesn’t
exist at load-time, all of its symbols will point to null. Then things are as
Pascal describes.
—Jens
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