Re: readonly property which is a mutable array
Re: readonly property which is a mutable array
- Subject: Re: readonly property which is a mutable array
- From: Remco Poelstra <email@hidden>
- Date: Fri, 19 Nov 2010 08:51:15 +0100
Op 19-11-2010 3:51, Ken Thomases schreef:
I of course want the items to be read only for the outside world, but the object itself should be able to modify it. Now the compiler complains about the properties not matching. How should I solve this? Make a custom getter that returns an immutable array? Make the property refer to a mutable array? Make the property an immutable array and make copies of the array while modifying it?
The ivar type and the property type don't have to match. In fact, there does not need to be any ivar backing whatsoever to properties.
Change your property declaration to NSArray *, and implement the getter with [[array copy] autorelease] or similar.
You don't need to implement the getter. The Cocoa docs are very clear that callers must respect the declared type of properties (i.e. return type of getters). That is, if the getter is declared to return an immutable NSArray, then callers must not interrogate the returned object to determine if it's really mutable nor invoke mutation methods on it. It may be, and often is (even in framework classes), that such a method returns an object that is, in fact, an NSMutableArray. That's an irrelevant implementation detail.
Thanks for the tips. Hope this will kill some warnings :)
Kind regards,
Remco Poelstra
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