Re: Why does Xcode define IBOutlet with @synthesize?
Re: Why does Xcode define IBOutlet with @synthesize?
- Subject: Re: Why does Xcode define IBOutlet with @synthesize?
- From: Charles Srstka <email@hidden>
- Date: Fri, 23 Sep 2011 21:49:16 -0500
On Sep 23, 2011, at 9:30 PM, Greg Parker wrote:
> On Sep 23, 2011, at 7:21 PM, Charles Srstka wrote:
>> On Sep 23, 2011, at 6:06 PM, Greg Parker wrote:
>>>
>>> Nib connection on iOS uses KVC. Nib connection on OS X does not use KVC itself, but it does use a similar "call method if it exists, set ivar directly if it does not" algorithm.
>>
>> But how does that work? If I make the IBOutlet an ivar, make it @private, and have +accessInstanceVariablesDirectly return NO, trying to access this ivar directly from another object causes a compiler error, and trying to access it via KVC throws a “not key value coding-compliant for the key <outlet name>” exception. Yet the nib loading mechanism is still able to set the ivar. I’ve always been curious about why exactly this works.
>
> On OS X, nib connection does not use KVC. Since it's not using KVC, it pays no attention to KVC machinery like +accessInstanceVariablesDirectly.
>
> The OS X nib connection implementation calls object_setInstanceVariable(). This function, like all of the runtime's introspection functions, ignores compile-time access controls.
Huh. I had always thought that those functions respected @private and @protected, but I just tried it, and you are indeed correct. Thanks.
It’s a little disturbing that private instance variables can be altered so easily, but then I suppose the same thing could just as easily be done by a third-party monkeying with the ivar in a category.
Charles_______________________________________________
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