Given an object foo of class Foo, I want to do the following:
NSString *key = @"some key";
id myObj = [foo valueForKey: key];
and have myObj equal to foo.
Is there a way to do this without defining a category on Foo?
views:
109answers:
2
+7
A:
The following works for me, returning foo:
id myObj = [foo valueForKey: @"self"];
Costique
2010-02-04 15:36:56
that's cool! I didn't know you could do that. =)
Dave DeLong
2010-02-04 16:01:34
Agreed, it is pretty darn cool, and it makes sense that you could ask for it this way. Is there a scenario where this is your only option, though? Perhaps you can only send a key path query to an object for which you don't have a pointer to its owning object? Sounds like an odd situation...
Quinn Taylor
2010-02-05 06:34:40
Yes, I admit I can't think of any real-world situation where I would really need this. But the coolness of @"self" is in its existence. I guess if you come across the rare case where you have to heavily rely on KVC, you will owe the engineer who did it a truckload of beer.
Costique
2010-02-05 07:07:57
I didn't know that this is possible, but if I think about it, it is not so surprising.
swegi
2010-02-05 08:01:22
@Quinn Taylor: it's good for sort descriptors that need a keypath, and you're sorting the actual object in the array, rather than a property of the object. i.e. an array of `NSNumber`
ohhorob
2010-07-08 21:08:32
Occam's Razor strikes again. I tend to agree with this answer — if you can get a pointer to message an object, just use that pointer. I understand this is probably just an academic exercise, but why spend cycles on key-value observing when the answer is obvious?
Quinn Taylor
2010-02-05 06:32:44