Re: KVO Response for incomplete paths

FROM : Mike Abdullah
DATE : Wed May 21 23:55:25 2008

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.
>>

>
> _______________________________________________
>
> Cocoa-dev mailing list (<email_removed>)
>
> 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/<email_removed>
>
> This email sent to <email_removed>