Difference between NSArray.array/.new /@[]/alloc-init

Question

There seem to be different methods of instantiating NSArrays (same for NSDictionary and some others).

I know:

1. [NSArray array]

Answer 1

1. [NSArray array] : Create and return an empty array

2. [NSArray new] : alloc, init and return a NSArray object

3. @[] : Same as 1.

4. [[NSArray alloc] init] : Same as 2.

Different between [NSArray array] and [[NSArray alloc] init] is if there are non-ARC:

• [NSArray array] is an autorelease object. You have to call retain if you want to keep it. E.g when you return an array.

• [[NSArray alloc] init] is an retained object. So you don't have to call retain more if you want keep it.

With ARC, they are same.