Re: copy vs mutableCopy?
Re: copy vs mutableCopy?
- Subject: Re: copy vs mutableCopy?
- From: Andreas Mayer <email@hidden>
- Date: Tue, 11 Jul 2006 18:44:41 +0200
Am 11.07.2006 um 18:07 Uhr schrieb Rob Ross:
As a followup, say I have an object with one instance variable, an
NSMutableString. And say some code calls -copy on this object.
You're saying that the intent is for an immutable copy? So I just
retain the ivar and copy the reference to a new object and return
that instance, even though the ivar is itself mutable? As the
implementor of the -copy method, I am trusting that the client will
not make changes to this value since it would affect another
instance? Is this correct?
And similarly, if -mutableCopy is called, I would make a deep copy
of the NSMutableString, even though it's already mutable, because
the intent of the caller is to modify that value and I don't want
the original object mutated? Is this also correct?
That really depends on the type of object.
It is my understanding, that mutableCopy is mostly used in
conjunction with collections.
Considering "normal" objects, the user will not modify any ivars
directly anyway, so there is no case for mutable/immutable copy here.
If you want the user to be able to modify a property on your object,
you will offer accessor methods to change the corresponding instance
variable. That will work, no matter if the previous value was
retained or copied.
Andreas
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