Re: Forcing a refresh on a bound control

FROM : Clark Cox
DATE : Sun May 18 12:34:32 2008

On Sun, May 18, 2008 at 3:20 AM, Christiaan Hofman <<email_removed>> wrote:
>
> On 18 May 2008, at 8:18 AM, mmalc Crawford wrote:
>

>>
>> On May 15, 2008, at 2:35 PM, Christiaan Hofman wrote:
>>

>>> You can force a KVO notification by sending a will/didChangeValueForKey:
>>> pair of messages.
>>>

>> As has been said on numerous occasions, no, don't do this.
>>

>
> I know it has been said. But I have never heard an alternative to forcing a
> KVO change notification.


IME, needing to "force" KVO notifications is a sign that my design is
deficient.

> Given that dependent keys can only be set for the
> same object...


FYI, while true for 10.4, this is no longer the case with 10.5. Check
out the +keyPathsForValuesAffectingValueForKey: method (and pay close
attention to the fact that the returned set contains key *paths* not
just keys).

<http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Protocols/NSKeyValueObserving_Protocol/Reference/Reference.html>

> And if you would think there may be an alternative in this
> particular situation (though I don't see it), I am talking about the general
> situation. Please proof me wrong, but I couldn't find it.


One can use KVO directly. As Malcom mentioned, one can have an object
observe whatever value the check box is bound to, and then, when a
change is registered, that object can set/change the appropriate value
in the model that is backing the text view.

--
Clark S. Cox III
<email_removed>