On May 21, 2009, at 2:15 AM, Quincey Morris wrote:
The obvious way of doing that is to bind 'Enabled' to the
NSObjectController's "selection" controller key, (no model key),
and use the value transformer NSIsNotNil. Anytime the selection is
not nil, the control is enabled… right? It's super simple, but it
doesn't work, and I don't see why not.
The documentation for [NSObjectController selection] says (in the
discussion):
If a value requested from the selection proxy using key-value
coding returns multiple objects, the controller has no selection,
or the proxy is not key-value coding compliant for the requested
key, the appropriate marker (NSMultipleValuesMarker,
NSNoSelectionMarker or NSNotApplicableMarker) is returned.
Otherwise, the value of the key is returned.
So nil is never returned (assuming none of the markers is defined to
be nil).
Thanks. I hadn't realized/remembered it worked that way. I might need
a refresher course on the finer details. :-)
You might try selectedObjects.count instead.
Yeah. Except there's no way to bind to that without a custom value
transformer like Sean said.
It did occur to me that I could bind to the selection controller key
and the "description" model key. Every object has a description. If
it's nil, then there is no selection. That works, but is unintuitive.
It seems like the proper thing to do would be to create a value
transformer "NSIsNoSelectionMarker"
I wish Apple would beef up the default set of value transformers. I've
had to write a few "obvious" ones.
Thanks guys,
--
Seth Willits
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