Is return (id)nil; valid?

Question

I want to return nil from a function that expects to get id. The compiler complains about this when I'm writing blocks. So, is it ok to return (id)nil;? Or am I misunderstanding something about what nil and id are?

@JoshCaswell: it says "Incompatible block pointer types sending `'void *(^)(void)'` to parameter of type `'id (^)()'`. — Claudiu, Sep 13 '13 at 01:00

score 4 · Accepted Answer · edited May 23 '17 at 10:31

4

It is valid. nil "should" be type of id (actually it is void * for some reason) but it is totally safe to cast nil to id. Similarly apply to 0 and NULL (they all just 0). And send message to 0 result defined behaviour (nop) so everything is fine.

I have the same problem about return nil in block and this is quote from the answer :

You're using an inferred return type for your block literal, but you don't have to.

The correct way to remove that error is to provide a return type for the block literal:

id (^block)(void) = ^id{
    return nil;
};

edited May 23 '17 at 10:31

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answered Sep 13 '13 at 00:58

Bryan Chen

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how do I specify the return type when I'm providing the block in-line to another function call? – Claudiu Sep 13 '13 at 01:00
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@Claudiu instead of `^{ return nil;}`, do `^id{ return nil;}` – Bryan Chen Sep 13 '13 at 01:05

Is return (id)nil; valid?

1 Answers1