Re: A Question on estimating +arrayWithCapacity
Re: A Question on estimating +arrayWithCapacity
- Subject: Re: A Question on estimating +arrayWithCapacity
- From: "Kyle Sluder" <email@hidden>
- Date: Fri, 9 Jan 2009 20:45:01 -0500
On Fri, Jan 9, 2009 at 8:40 PM, Graham Cox <email@hidden> wrote:
> Isn't guaranteed by the semantics of inheritance? I've specified the class:
> [NSMutableArray ... and what I want it to give me... array]; And the fact
> that NSMutableArray inherits NSArray ensures that anything that array can
> do, NSMutableArray can do.
No, it means that NSMutableArray responds to everything NSArray
responds to; there's no semantic guarantee. What if the subclass
needs a different designated initializer, maybe one with more
arguments? It would make sense for it to override the superclass's
designated initializer to throw an exception. But without overriding
the convenience constructor, this will blow up.
--Kyle Sluder
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