I may not have made myself clear enough: I need objects bound to this property to be notified whenever the selection of the array controller changes, much like the existing "canAdd:" and "canRemove:" properties of NSArrayController. This property has nothing to do with whether or not the array controller CAN change the index set; the default behavior of removeSelection: is fine with me.

- Alex

On Jul 28, 2009, at 10:29 PM, Chase Meadors wrote:

I'm assuming you've written an accessor that makes the appropriate judgments based on selectionIndex and selectionIndexes. It's not getting called, however, because the framework doesn't know it's there! I would override removeSeletion: like so:

- (void)removeSelection:(NSIndex *)index { //maybe not exact wording, but whatever

        if ([self canRemoveSelection]) {

                [super removeSelection:index];

        }

}

On Jul 29, 2009, at 12:09 AM, Alexander Heinz wrote:

Hello all,

I've got an NSArrayController subclass with a computed property:

@property (readonly) BOOL canRemoveSelection;

(This basically adds some application-specific checks to the canRemove: property, so that I can bind a "remove" button in Interface Builder.)

I want the property to be recomputed every time the "selectionIndex" or "selectionIndexes" of the array controller change, so, in my ".m" file, I have:

+ (NSSet*)keyPathsForValuesAffectingCanRemoveSelection
{
return [NSSet setWithObjects:@"selectionIndex", @"selectionIndexes", nil];
}

(I realize this is probably redundant, but bear with me.)

However, the accessor for the property (i.e., "- (BOOL)canRemoveSelection") is never called, beyond the initial call when the object is created. As a result, the button bound to the property never changes state.

I've checked to make sure that -setSelectionIndexes: is being called, and it is, but the property is not re-computed.

Does anyone see anything immediately wrong here?

- Alex

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