Re: Retain/Release and Properties clarification
Re: Retain/Release and Properties clarification
- Subject: Re: Retain/Release and Properties clarification
- From: Bayes Scott F <email@hidden>
- Date: Wed, 12 Oct 2011 09:21:01 -0700
Someone on Matt's site mentioned the possibility that the synthesized ivar could be implemented indirectly, say as a member of a collection. Since the implementation's opaque, we don't know if that ever can happen.
So, is self->mySynthIvar safe (both lvalue and rvalue), or should we be messaging?
And does the compiler ever shortcut something like self.mySynthSimpleIntVar to self->mySynthSimpleIntVar, or does it always use the setter/getter?
Thanks
ScottB
On Oct 11, 2011, at 10:12 , David Duncan wrote:
> On Oct 11, 2011, at 9:57 AM, Matt Neuburg wrote:
>
>> I did everything "right" when I named an ivar "firstResponder" (property, synthesized ivar, synthesized accessors) and totally broke my app because Apple was apparently already using an undocumented ivar called "firstResponder".
>>
>> http://www.cocoabuilder.com/archive/cocoa/296662-assign-property-behaves-differently-from-simple-instance-variable.html
>
> The problem wasn't an undocumented ivar, it was an undocumented method. The @synthesize thus overrode the existing method and broke your project because parts of UIKit were expecting the default implementation and got your implementation instead.
>
> As a rule, we strive to avoid this situation, but unfortunately this does happen on occasion.
>
>> Also, note that there are circumstances where a synthesized ivar won't work; see, for instance, this note:
>>
>> http://www.cocoabuilder.com/archive/cocoa/298320-inherited-implicitly-created-member-is-no-member.html
>
> The gist of this is that synthesized ivars are private, and the public interface (the @property) doesn't tell you about private implementation details (the ivar). As such, subclasses can't get at synthesized ivars, precisely because the @synthesize declaration is hidden from them.
> --
> David Duncan
>
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