Re: KVO Response for incomplete paths
Re: KVO Response for incomplete paths
- Subject: Re: KVO Response for incomplete paths
- From: Mike Abdullah <email@hidden>
- Date: Wed, 21 May 2008 22:55:25 +0100
On 21 May 2008, at 22:15, Gordon Apple wrote:
So what you are saying (if I understand it correctly) is that
once you
try to observe the property at that path, the intercept mechanism
for the
property set-accessor is actually put into place, along with its
before/after notifications, and will notify properly when the path is
actually viable. That is good news. So I should be able to rule
that out
and look elsewhere for problems I am encountering.
Yes. It's not a question of the path being "viable." KVC/KVO is
designed to accommodate nil values as just another perfectly
reasonable value. Part of the beauty of being able to happily message
nil under ObjC.
On 21 May 2008, at 19:51, Gordon Apple wrote:
OK, thanks. That helps on the KVO responses. However, I have
other
questions about the entire KVO process.
Not having access to the innards of KVO, I wonder how dymanic the
process is. For example, my inspector bindings are through an
object
controller which binds through MSApp.mainWindow which seems to
successfully
switch its focus to a new main window with no problems. This, to
me,
indicates that the process operates dynamically according to the
path,
rather than statically binding when it is set up.
So my new question is whether or not I can successfully observe a
property that does not exist at registration time, and then have it
observe
properly when the path is created. E.g., register to observe
xxx.shadow.angle when shadow does not exist, then add the shadow
object and
have xxx.shadow.angle be observed properly.
As long as xxx returns nil for -valueForKey:@"shadow" initially, and
then puts out proper KVO notifications when a shadow comes into
being,
this works just fine.
Mike.
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