Re: Overriding -copyWithZone: the right way
Re: Overriding -copyWithZone: the right way
- Subject: Re: Overriding -copyWithZone: the right way
- From: Jonathon Mah <email@hidden>
- Date: Sat, 6 Nov 2004 04:54:25 +1030
On 6 Nov 2004, at 03:16, Michael Becker wrote:
I have a subclass of NSCell (for a TableView) that is supposed to
display an image and an NSPopUpButtonCell. Everything works fine so
far, but I obviously need to override -copyWithZone:. Here's what I
came up with:
- (id)copyWithZone:(NSZone *)zone {
PCShoppingCartCell *copy = [[ PCShoppingCartCell alloc]
initImageCell:nil];
return copy;
}
This does not crash, but it looks so suspiciously memory-leaking...
(the alloc/init is not paired with a release on my side).
As far as I'm aware, returning a copy with retain count 1 is the right
thing to do. As you probably know, you need to pair alloc/release, as
well as copy/release (in other general code). Therefore a copied object
must be returned with a retain count of 1, or it'd be over-released.
When trying to follow the (few) suggestions the docs give me, I tried
this (but it did not work, the app crashed as soon as the TableView
wanted to redraw):
- (id)copyWithZone:(NSZone *)zone
{
PCShoppingCartCell *copy = [super copyWithZone:zone];
[ copy _initSubCells]; // This inits and sets up the NSPopUpButtonCell
return copy;
}
What you're doing there is calling copyWithZone: on the superclass,
NSCell. This returns an NSCell (which wouldn't implement your own
_initSubCells method), not a PCShoppingCartCell.
Jonathon Mah
email@hidden
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