On May 27, 2010, at 05:59, Ariel Feinerman wrote:
> my question is: what does -copy for immutable
> variant of immutable/mutable objects, for instance NSArray *arrayCopy =
> [array copy]; returns true copy or retains one?
The class of the variable 'arrayCopy' is irrelevant. If the instance being
copied is a (subclass of) NSMutableArray, then it will use NSMutableArray's
'copy' implementation, which makes a "true" copy.
If the instance being copied is a (immutable subclass of) NSArray, then it will
use NSArray's 'copy' implementation, which returns a retained reference to the
original object.
Note that both of these behaviors are implementation details which are *not*
guaranteed by the API.
> Or what does happen if
> object itself is immutable and has not setters, but it instance variables is
> mutable and can be changed?
There's no built-in behavior that applies to every class. It's up to each class
to provide an implementation of 'copy:' (well, actually 'copyWithZone:') if it
wants to conform to the NSCopying protocol. The current behavior of the Cocoa
collection classes is as described above. The 'copy' behavior of other objects
can only be described on a case-by-case basis.
You should take a look at the NSCopying Protocol Reference:
http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Protocols/NSCopying_Protocol/Reference/Reference.html
for a more detailed answer to your question.
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