> On Apr 24, 2017, at 1:17 PM, Quincey Morris > <quinceymor...@rivergatesoftware.com> wrote: > > On Apr 24, 2017, at 10:11 , Charles Srstka <cocoa...@charlessoft.com > <mailto:cocoa...@charlessoft.com>> wrote: >> >> What Quincey seemed to be referring to was a property that was not backed by >> any kind of persistent value. > > That wasn’t actually the kind of property I had in mind. I was thinking of > settable, computed properties that did not depend on the value(s) of other > KVO-observable properties. There probably aren’t many plausible *simple* > examples, but I was thinking of such cases as when the value is stored in an > I/O device rather than RAM, or when the value is retrieved from a server.
In this case, I would try to see if I could find some way to monitor changes in the underlying storage, and call the willChange and didChange methods manually when changes occur. I’d only make the property dynamic if it was completely impossible to do this, and I’d keep this to a last resort. The reason is because in this case, the property is not fully KVO-compliant, because its value can change without notifications being sent. I did kind of touch on this with the UserDefaults-example I provided a while back. Pretending that NSUserDefaults still notified via NSNotifications only, as was the case before native KVO support was added to it, you would register for the NSNotification, check whether your default had changed, and fire the willSet and didSet notifications once it did. This is a lot more robust than depending on the automatic notifications when your property’s value may change without going through the property’s setter. Charles _______________________________________________ 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: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
