On Aug 18, 2010, at 18:00, Frank D. Engel, Jr. wrote:
> I have a controller class which is represented as a simple object (cube icon)
> in Interface Builder. This class has an "id" field to which I assign various
> instances of core data entities (represented by a subclass of NSManagedObject
> by selecting them in an NSBrowser whose delegate is the controller class.
>
> I then have an NSSlider and an NSCheckbox which both have their value
> bindings bound to the same field of the selected object, via the controller
> class; in other words:
>
>
> @interface MyBrowser : NSObject
> {
> id selectedWhatever;
> }
>
> - (id)selectedWhatever;
> - (void)setSelectedWhatever:(id)whatever;
>
>
>
> Then the "value" bindings of the NSSlider and NSCheckbox are both
> "selectedWhatever.someField".
>
>
> The problem I am having is that if I move the slider, the value of the field
> does not change right away, but if I select something else and then select
> the modified entity again (changes selectedWhatever to something else and
> back), the field shows the modified value.
>
> It almost seems as if the slider is not sending updates to the entity until
> the entity is about to change?
>
> Similarly, if I edit the value in the text field, the slider does not move
> until I select something else then come back.
>
> How can I get the text field and slider to update in sync with each other?
>
>
> If it helps, the class being used for the "selectedWhatever" values has the
> field defined as:
>
> @property float someField;
Since your property is declared to have a scalar (float) value, it must be a
custom accessor of your custom NSManagedObject subclass. (Core Data's
internally-provided properties are all object values, never scalars.) See
"Scalar Values" in:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreData/Articles/cdNSAttributes.html#//apple_ref/doc/uid/TP40001919-SW13
That means you've probably forgotten to implement KVO compliance in the setter
for this property. (Overridden Core Data setters must invoke
didChange/willChangeValueForKey: explicitly.) See "Custom Implementation" in:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreData/Articles/cdAccessorMethods.html#//apple_ref/doc/uid/TP40002154-SW1
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