Re: Binding/KVC : valueForKey: and NSDictionary (was: valid accessor for framework objects. (was: implicit and explicit invocation of description method))

FROM : Max Barel
DATE : Tue Oct 05 23:29:40 2004

Le 5 oct. 04, à 15:54, Max Barel a écrit :

> In a more general description:
> - The NSArraycontroller manage an array of NSScreen (tried both
> NSArray and mutable copy).
> - Its object class is defined as NSScreen.
> - NSScreen objects have a property named deviceDescription, of class
> NSDictionary.
>
> No accessor of the form selection.deviceDescription.amethod[an
> NSArraycontroller] works.
> Accessors of the form selection.deviceDescription.aKey (e.g
> selection.deviceDescription.NSDeviceSize) work once. Changing the
> initial selection crash on signal 10.
>
> Can we suspect a weird behavior with NSDictionary to-one relationship?


After more testing and cross-reading of the valueForKey: method
documentation, I come with a differently formulated question:

The valueForKey: method is defined in the NSKeyValueCoding protocol of
NSObject. It is also overloaded in NSDictionary.

Is the NSDictionary version of the method conforming to the
NSKeyValueCoding?
I understand that the overloaded version add the ability to find a
value from a key (in the NSDictionary sense), but it is still able to
find a public method, as stated by the first rule of KVC:

valueForKey:
- (id)valueForKey:(NSString *)key
...
The default implementation works as follows:
   1.     Searches for a public accessor method based on key. For example,
with a key of “lastName”, valueForKey: looks for a method named
getLastName or lastName
...

For example, none of the test I made allowed me to access the value
from the -count method of an NSDictionary object using KVC.

Max