Re: copy and mutableCopy
Re: copy and mutableCopy
- Subject: Re: copy and mutableCopy
- From: John McCall <email@hidden>
- Date: Sun, 27 Apr 2014 02:06:19 -0700
On Apr 27, 2014, at 2:00 AM, Dave <email@hidden> wrote:
> A long time back, I remember reading something about the way in which copy and mutableCopy are implemented. I think basically it said that:
>
> someObject = [someOtherObject copy];
>
> or
>
> someObject = [someOtherObject mutableCopy];
>
> Wouldn’t necessarily allocate any extra data storage. I’ve been searching for it to refresh my memory, but I can’t see to find it anywhere. Does anyone know if this document or something like it exists somewhere?
I don’t know if there’s a document, and like a lot of things with ObjC the actual guarantees are pretty weak, but implementations of these methods on immutable types have been turning into essentially “return [self retain];" for quite some time. But that’s when the actual dynamic type is guaranteed-immutable, e.g. something constructed as an NSArray, not just something that’s immutable by convention, e.g. an NSMutableArray that you’re passing around as an NSArray.
John.
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