Question

As I assumed, this should work’s fine for immutable object under ARC:

- (id) copyWithZone:(NSZone *)zone {
    return self;
}

But if I need deep copy, I should write something like this:

- (id) copyWithZone:(NSZone *)zone {
    Immutable *copy = [[Immutable alloc] initWithStr:str];
    return copy;
}

So, If I assumed right, ARC would understand situation (1) and (2) and make right decision about “+1” for references.

Am I right ?

Answer 1

Seems I’m right: I can’t find any concrete documentation on topic, but I create separate test project with ARC turned off, then choose migrate to ARC. Here is code without ARC:

- (id) copyWithZone:(NSZone *)zone {
    return [self retain];
}

This is what I got after migration:

- (id) copyWithZone:(NSZone *)zone {
    return self;
}

It’s a magic how ARC works sometimes, but seems we should just believe it will doing it’s job well. 🙂