Master-Detail binding in User Defaults

FROM : Steve Nicholson
DATE : Wed Apr 23 02:47:42 2008

I'm trying to set up a Master-Detail binding with User Defaults under 
OS X 10.4.11. It is correctly reading values I manually put into the 
Preferences file. I can select different items in the table and the 
detail items display the correct information, but no changes are 
written to the file. If I add an item to the array (using a button 
connected to the NSArrayController's insert: action), an item is 
added to the table. I can edit the name of the item in the table and 
change its details and see those changes if I select another table 
item the select the new one again, but when I quit my program and 
look at the preferences file, an empty dictionary has been added to 
the array.

I also have "normal" preference items in the same window that work fine.

Is there something I'm doing wrong or is this just not a supported 
usage?

Here's the setup in Interface Builder:

NSArrayController:
   Name: Variables
   Object class Name: NSMutableDictionary
   contentArray bindings:
       Bind to: Shared User Defaults
       Controller Key: values
       Model Key Path: variables

NSTableColumn value bindings:
   Bind to: Variables (NSArrayController)
   Controller Key: arrangedObjects
   Model Key Path: name

NSPopUpButton selectedIndex bindings:
   Bind to: Variables (NSArrayController)
   Controller key: selection
   Model Key Path: lineWidth

NSPopUpButton selectedIndex bindings:
   Bind to: Variables (NSArrayController)
   Controller key: selection
   Model Key Path: lineSymbol

Relevant contents of Preferences file (the second array element is an 
empty dictionary that was inserted with the NSArrayController's 
insert: action):

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://
www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
   <key>variables</key>
   <array>
       <dict>
           <key>lineSymbol</key>
           <integer>8</integer>
           <key>lineWidth</key>
           <integer>2</integer>
           <key>name</key>
           <string>R</string>
       </dict>
       <dict/>
       <dict>
           <key>lineSymbol</key>
           <integer>1</integer>
           <key>lineWidth</key>
           <integer>1</integer>
           <key>name</key>
           <string>PRES</string>
       </dict>
       <dict>
           <key>lineSymbol</key>
           <integer>12</integer>
           <key>lineWidth</key>
           <integer>3</integer>
           <key>name</key>
           <string>RHO</string>
       </dict>
   </array>
</dict>
</plist>