Re: triggerChangeNotificationsForDependentKey in subclass of NSArrayController
Re: triggerChangeNotificationsForDependentKey in subclass of NSArrayController
- Subject: Re: triggerChangeNotificationsForDependentKey in subclass of NSArrayController
- From: Gabriele de Simone <email@hidden>
- Date: Thu, 7 Oct 2004 13:44:11 -0400
On Oct 7, 2004, at 12:09 PM, Shaun Wexler wrote:
On Oct 7, 2004, at 8:57 AM, Gabriele de Simone wrote:
Esteemed members of the Cocoa Bindings cult,
It seems that if I add a new key to an NSArrayController and make
"arrangedObjects" dependent on that key, the change notifications
when the key is modified are never sent (or at least my views
dependent on "arrangedObjects" don't get updated). Here's the
scenario:
+ (void) initialize {
[self exposeBinding:@"myKey"];
[self setKeys:[NSArray arrayWithObjects:@"myKey", nil]
triggerChangeNotificationsForDependentKey:@"arrangedObjects"];
}
+ (BOOL)automaticallyNotifiesObserversForKey:(NSString *)key {
if ([key isEqualToString:@"myKey"]) {
return NO;
}
return [super automaticallyNotifiesObserversForKey:key];
}
- (void) setMyKey:(NSString*)myKey {
if (_myKey != myKey) {
[self willChangeValueForKey:@"myKey"];
_myKey = [myKey copy];
[self didChangeValueForKey:@"myKey"];
}
}
The obvious solution is to call [self rearrangeObjects] in the setter
method, but I am more interested in knowing whether I have
misunderstood/ignored some properties of NSControllers.
How are you going to automatically trigger a change notification for
that key, if you disable automatic notification for the key?!! Use
one or the other. It's okay to send your own -rearrangeObjects
message in the setter if you prefer. Are you just trying to avoid
rearranging unnecessarily, if the setter is called with the same key?
BTW, it might be better to use isEqualToString: rather than compare
pointers, since you're making a copy.
Shaun,
I think you are misunderstanding what
automaticallyNotifiesObserversForKey: does. If you return NO, you are
just declaring the intention to call willChangeValueForKey: and
didChangeValueForKey: yourself (which is what I am doing in the
example). Even if I change my code to return YES for myKey (from
automaticallyNotifiesObserversForKey: of course), the notification for
the dependent key is not sent.
Again, the point of the question is not that I don't want to call
rearrangeObjects, but to understand why the notification is not being
triggered.
Gabe
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