On Dec 18, 2009, at 2:28 PM, Kyle Sluder wrote:
On Fri, Dec 18, 2009 at 11:18 AM, Paul Bruneau <paul_brun...@special-lite.com> wrote:if ([keyPath isEqualToString:kOverallWidth]) { [self willChangeValueForKey:@"overallWidth"];NSLog(@"got notification that overallwidth changed:%@", object); [self didChangeValueForKey:@"overallWidth"]; }Please note that it is not correct to call -will/didChangeValueForKey: without actually changing the value. The KVO mechanism might just simply not send a notification at all. (Well, I guess it's valid, but you might see fewer observation notifications than you would expect.) This is difficult to get right with derived properties. Also don't have the first inclination I had, which is to use -keyPathsForValuesAffectingValueForKey:. As described in the documentation, it will not work.
Ugh, so I guess you are saying that derived properties are not trustworthy in this usage?
I like them so much because then I never have to worry about the stored value being out of date (which admittedly, if I do everything exactly right, I guess it will never be out of date, but I like not having to worry about it).
It's also a bummer because so far it is working fabulously with willChange/didChange.
I might live dangerously and leave it in until it bites me. Thanks for the warning, I'll make note of it. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
