One possible issues is that `self.thingy=x;` will trigger two change
notifications for `thingy`: one for `self.dictionaryOfThings = temp;` (due to
keyPathsForValuesAffectingThingy), and one when the setter exits. Depending one
what your observer does this may have unforeseen side effects.
A possible workaround would be to replace `self.dictionaryOfThings = temp;`
with `_dictionaryOfThings = temp;`.
Gerd
>
> On Nov 17, 2015, at 19:18, Graham Cox <graham....@bigpond.com> wrote:
>
> I’m using KVO to observe a bunch of properties.
>
> Most of these properties are split out into simple things that set a single
> value, but internal to my object, some end up setting a common dictionary of
> attributes, which is also a property.
>
> I KVO observe both the simple properties and the common dictionary property.
> Mostly this is working, but when code directly sets the dictionary property,
> the other properties don’t trigger their observers, even though I’m
> implementing the +keyPathsForValuesAffecting<property>, which I believe
> should cause the additional triggering. Have I understood that right?
>
> Here’s the kind of code I have:
>
>
> @property (retain) id<NSObject> thingy;
> @property (retain) NSDicitonary* dictionaryOfThings;
>
> @implementation
>
> - (void) setThingy:(is<NSObject> thing
> {
> NSMutableDictionary* temp = [self.dictionaryOfThings mutableCopy];
> [temp setObject:thing forKey:kThingKey];
> self.dictionaryOfThings = temp;
> }
>
> - (id<NSObject>) thingy
> {
> return [self.dictionaryOfThings objectForKey:kThingKey];
> }
>
>
> + (NSSet*) keyPathsForValuesAffectingThingy
> {
> return [NSSet setWithObject:@“dictionaryOfThings”];
> }
>
>
> So what I want (expect?) is that is code sets -dictionaryOfThings directly,
> an observer of ‘thingy’ will be triggered. Is that right?
>
>
> —Graham
>
>
>
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