title: ArrayController's CoreData selection binding not refreshed across multiple NIB files
body: <p>I've a hard time getting my Cocoa application to work as expected. It consists of a toolbar in the <strong><em>main.nib</em></strong> and a custom view in a <strong><em>details.nib</em></strong> file. Now I want the user to select an entry in a NSPopupButton in the toolbar and the content of the custom view should be changed accordingly.</p>
  
  <p>To achive this I've added an ArrayController to my <strong><em>main.nib</em></strong>, showing the following configuration:</p>
  
  <p><img src="https://i.stack.imgur.com/ED3PW.png" alt="Attributes Inspector for Array Controller">
  <img src="https://i.stack.imgur.com/JYRWs.png" alt="Managed Object Context Configuration"></p>
  
  <p>Furthermore the Managed Object Context is bound to the Model Key Path <strong><em>delegate.managedObjectContext</em></strong> (it is no document based application).</p>
  
  <p>With this configuration the NSPopupButton works just fine and if I add a Label to the toolbar (also in the main.nib) and bind it's value to the selection (Controller Key), name (Key Value Path) the content is refreshed whenever I change the selection.</p>
  
  <p>The Bindings of the NSPopupButton look like shown in the following screenshot:
  <img src="https://i.stack.imgur.com/I8wFT.png" alt="NSPupupButton Bindings"></p>
  
  <p>So in my <strong><em>details.nib</em></strong> I tried the following to achieve the same effect. I've added an ArrayController, whichs Managed Object Context is also bound to the Model Key Path <strong><em>delegate.managedObjectContext</em></strong>. Also the configuration is exactly the same as shown in the above pictures. I've then added a label and bound it's value to the selection (Controller Key), name (Key Value Path) of this ArrayController.</p>
  
  <p><img src="https://i.stack.imgur.com/srTST.png" alt="Label Bindings"></p>
  
  <p>The problem is that the Label only displays the the initial selection after the application did launched correctly. Afterwards, when I change the selection of my NSPopupButton, the label does not change accordingly.</p>
  
  <p><img src="https://i.stack.imgur.com/GqhWY.png" alt="enter image description here"></p>
  
  <p>What are my options to get the ArrayController working accross multiple NIB files?</p>
  
  <p>BTW: I've tried to follow <a href="http://appledoc.gentlebytes.com/blog/2009/09/02/coredata-bindings-multiple-nibs/" rel="nofollow noreferrer">this blog post</a> to get it working but it seems I'm missing something here.</p>
  
  <p><strong>Update:</strong>
  If I replace the Label in the <strong><em>details.nib</em></strong> by a NSTextField and change the text of it, the changes are reflected in the related NSPopupButton entry. So I guess I made something right, but the main problem remains: I can only edit the entry which was loaded during application startup. Switching to another NSPopupButton entry does not change the text in the NSTextField.</p>
  
  <p><strong>Update 2:</strong>
  I've created a small sample project with exactly the same configuration and uploaded it on <strong><a href="https://github.com/Restage/ACBindingExample" rel="nofollow noreferrer">GitHub</a></strong>. So feel free to check it out or create a pull request with a solution approach.</p>