Look for "Cocoa Bindings Guide" in the docs. It would be nice if it were
cross-referenced in every class description. SelectedIndex should work for a
segmented control. Haven't tried it myself though.
Cheers,
Dave
On 2010-01-10, at 10:58 PM, Jerry Krinock wrote:
> After studying some about bindings during the last week, I decided that, just
> for fun, I would bind an NSSegmentedControl to its window controller using a
> binding instead of target/action. I thought that selectedSegment might be a
> KVO-compliant property of NSSegmentedControl because it has a
> -selectedSegment and -setSelectedSegment: method.
>
> So I exposed a binding named @"foo" in my window controller's +initialize, in
> -awakeFromNib I added this:
>
> [windowController bind:@"foo"
> toObject:segmentedControl
> withKeyPath:@"selectedSegment"
> options:0] ;
>
> and finally in a "windowWillClose" cleanup method I added an unbind:.
>
> The above code compiled and ran without any bitchin' from out of the console,
> and at any time in the program if I send -infoForBinding:@"foo" to
> windowController, I log the expected result:
>
> bindingInfo = {
> NSObservedKeyPath = selectedSegment;
> NSObservedObject = <NSSegmentedControl: 0x1b879c90>;
> NSOptions = {
> NSMultipleValuesPlaceholder = <null>;
> NSNoSelectionPlaceholder = <null>;
> NSNotApplicablePlaceholder = <null>;
> NSNullPlaceholder = <null>;
> NSRaisesForNotApplicableKeys = 1;
> NSValueTransformer = <null>;
> NSValueTransformerName = <null>;
> };
> }
>
> But it "just didn't work". Flipping that segmented control in the user
> interface never caused my window controller's -setFoo: to run.
>
> Did I do anything wrong?
>
> If not, I conclude that NSSegmentedControl's is not KVO-compliant for
> property 'selectedSegment'. That is, the class implementation probably
> changes the view without invoking the setter.
>
> I changed to target/action and it works fine.
>
> So how does one know whether a property in Cocoa class is KVO-compliant? I
> can't find an answer in the Key-Value Observing Programming Guide. I thought
> maybe there's a little point system:
>
> 1. Property has a setter and getter; i.e. -bar and -setBar:. Add 2 points.
> 2. I remember seeing, every now and then, in newer API documentation, a
> notation that this "property is observeable", or something like that. Add 8
> points.
> 3. Add 1 point for each Mac OS X dot release that the class first appeared
> in. 0 points for 10.0, 1 point for 10.1, etc.
> 4. If the class is a "view layer" class, subtract 2 points. Most people
> don't usually bind to view classes.
> 5. Test it and see if it works. Add 5 points. What is the possibility that
> it could stop working in a future Mac OS X release?
>
>
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