Re: Using bindings to make an NSPopupButton to assign an array filter predicate
Re: Using bindings to make an NSPopupButton to assign an array filter predicate
- Subject: Re: Using bindings to make an NSPopupButton to assign an array filter predicate
- From: James Farwell <email@hidden>
- Date: Mon, 18 Dec 2006 10:58:15 -0800
On Dec 18, 2006, at 10:40 AM, Matt Neuburg wrote:
On Sun, 17 Dec 2006 16:34:25 -0800, James Farwell <email@hidden>
said:
Greetings,
I am attempting to use Cocoa Bindings in an app for the first time
and I'm running into a bit of a roadblock. I have a list of data
that can be filtered a few different ways, and I would like to let
the user select how it is filtered via an NSPopupButton in my
preferences window. I have an NSArrayController (dataController)
managing the list of data, and another NSArrayController
(predicateController) managing an list of predicates that define the
different ways to filter. I am trying to figure out how to set up
the Cocoa Bindings in such a way that selecting a different item in
the NSPopupButton will cause the dataController to immediately apply
the new predicate as its filter. Here is what I have so far:
predicateController (NSArrayController)
-----
contentArray
Bind to: controllerAlias
Controller Key: selection
Model Key Path: predicates
-----
dataController (NSArrayController)
-----
contentArray
Bind to: controllerAlias
Controller Key: selection
Model Key Path: data
-----
filterPredicate
Bind to: predicateController
Controller Key: selection.predicate
-----
NSPopupButton
-----
content
Bind to: predicateController
Controller Key: arrangedObjects
-----
contenValues
Bind to: predicateController
Controller Key: arrangedObjects
Model Key Path: name
-----
selectedIndex
Bind to: Shared User Defaults
Controller Key: values
Model Key Path: filter
-----
When I build/run this, the NSPopupButton populates properly, and my
data shows up filtered by the first predicate in the list, regardless
of which is selected. If I try to change the selection of the
NSPopupButton, the visible data does not change.
I can only assume that the NSPopupButton is not actually setting the
"selection" of its content NSArrayController. My question is, does
anyone know either how to get this scenario to work, or an example
that does something very similar correctly.
Remember, bindings are basically nothing but observing (KVO). Thing
A can
"see" Thing B change because (1) Thing A is observing Thing B and
(2) Thing
B changes in a KVO-compliant way. So, in your scenario, what is
observably
changing? You complain that when the user chooses from the
NSPopupButton,
the predicateController's selection is not changing. Well, what
would cause
it to change? You've bound the NSPopupButton's selectedIndex to the
shared
user defaults - you've not connected it in any way to the
predicateController.
For the standard way of hooking things up, check the archives:
<http://www.cocoabuilder.com/archive/message/cocoa/2006/5/31/164724>
m.
--
matt neuburg, phd = email@hidden, <http://www.tidbits.com/matt/>
A fool + a tool + an autorelease pool = cool!
AppleScript: the Definitive Guide - Second Edition!
<http://www.amazon.com/gp/product/0596102119>
Right you are. Since all the basic bindings tutorials I had read
were covering table views I made the mistake of assuming that all the
behind-the-scenes magic that occurs when you bind a table view column
to a controller (which must somehow set up a reverse binding so that
the controller can observe the table view's selection changes) also
worked for popup buttons. Thanks for the response!
- James
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