Why alloc return nil? ( Objective-C )

Question

I am porting iOS opengl games to metal

Use metalangle https://github.com/kakashidinho/metalangle

I use pre-compiled dynamic library

Return nil when creating MGLContext

MGLContext * aaa = [MGLContext alloc];

aaa == nil

Why is that?

I thought alloc would return nil only when the memory overflowed

Answer 1

In modern ObjC, it is not well-defined to only call +alloc without then calling an init method:

You must use an init... method to complete the initialization process. For example:

TheClass *newObject = [[TheClass alloc] init];

It was never a good practice, but you now cannot split up allocation and initialization.

That said, how are you testing this? I haven't been able to reproduce it so far. It is possible that MGLContext itself is nil. That would happen if the dynamic library is weakly linked, and not present.

Answer 2

This is a problem caused by a "weakly linked"

Thanks @RobNapier

Thank you all

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