Re: Toll-free bridge type at runtime
Re: Toll-free bridge type at runtime
- Subject: Re: Toll-free bridge type at runtime
- From: Michael Ash <email@hidden>
- Date: Thu, 2 Apr 2009 16:54:26 -0400
On Thu, Apr 2, 2009 at 3:20 PM, Marcel Weiher <email@hidden> wrote:
>
> On Apr 1, 2009, at 21:44 , Michael Ash wrote:
>
>> On Thu, Apr 2, 2009 at 12:33 AM, Ryan Joseph
>> [distinguishing between NSArray and CFArray]
>> The test cannot be performed, because the question does not make any
>> sense.
>
> While this answer is mostly true for what the original poster is trying to
> accomplish (as far as I can tell), it is actually not true.
>
> An NSCFArray and a CFArray are indistinguishable as described, and if you as
> for an NSArray, you will typically get an NSCFArray.
>
> However, an actual NSArray that is not an NSCFArray will be different and
> distinguishable. This distinction is also not just academic, but quite
> important because it is used by CoreFoundation to know wether to call its
> own functions or send a message to the object in question, allowing custom
> NSArray subclasses to be used in CFArray calls.
No, you're examining an entirely different question, which is whether
a particular object is the built-in provided NSArray subclass or a
custom subclass. Of course you can tell those apart, just like you can
distinguish between an NSTextField and an NSButton. But they're *both*
NSViews, and any NSArray subclass is still an NSArray. And any NSArray
is also a CFArray. It may have a different implementation from the
normal CFArray, but there's nothing weird about that: welcome to
object oriented programming.
>> An NSArray is a CFArray. A CFArray is an NSArray. You can't take one
>> of them and ask which one it is any more than you can ask your friend
>> whether he's Bob or Bill. They're just two names for the same thing.
>
> s/NSArray/NSCFArray/g
No. Please, if you disagree, just state your position, don't modify mine.
Mike
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