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Editorial Team
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Asked: 2026-05-14T00:56:42+00:00

When I bind a control to an NSArrayController using Interface Builder, there are a

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When I bind a control to an NSArrayController using Interface Builder, there are a variety of options under the “Controller Key” field in the bindings inspector.

I understand what “arrangedObjects” is, and I semi-understand what “selection” is, but I’d love to see a really nice explanation of all the options and when to use each one. The list includes: selectionIndexes, selectionIndex, selectedObject, sortDescriptors, etc. I haven’t been able to find a good explanation of these options.

I’m having trouble with a button that’s bound to target > selection, so I’m hoping a much deeper understanding of these Controller Keys might help me debug my issue.

Thanks!!!

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  1. Editorial Team

    These are tricky to find. They seem to be referenced everywhere by various Cocoa books, and even Apple’s docs, but I haven’t seen anyone unify an explanation of them into a single location. The answer is, Apple defines them inside the docs for each controller class:

    • NSObjectController (doc)
    • NSArrayController (doc)
    • NSDictionaryController (doc)
    • NSTreeController (doc)
    • NSUserDefaultsController (doc)

    These docs are also useful:

    Inheritance for these “Controller” objects looks like so (this is important to discover where some of the “Controller Key” options come from):

    NSController -> NSObjectController
NSController -> NSObjectController -> NSArrayController
NSController -> NSObjectController -> NSArrayController -> NSDictionaryController
NSController -> NSObjectController -> NSTreeController
NSController -> NSUserDefaultsController

// Note:  NSController is an abstract class (don't worry about it).  It inherits from NSObject.

    If you find a Controller Key not defined in the docs for a particular class, it’s probably defined in its superclass. Below are all the Controller Keys available for each of the above (Xcode 3.2.1, Interface Builder 3.2.1):

    // **NSObjectController**
canAdd
canRemove
isEditable
selectedObjects
selection


// **NSArrayController**
arrangedObjects
canAdd
canInsert
canRemove
canSelectNext
canSelectPrevious
filterPredicate
isEditable
selectedObjects
selection
selectionIndex
selectionIndexes
sortDescriptors


// **NSDictionaryController**
arrangedObjects
canAdd
canInsert
canRemove
canSelectNext
canSelectPrevious
filterPredicate
isEditable
selectedObjects
selection
selectionIndex
selectionIndexes
sortDescriptors


// **NSTreeController**
arrangedObjects
canAdd
canAddChild
canInsert
canInsertChild
canRemove
isEditable
selectedObjects
selectedNodes
selection
selectionIndexPath
selectionIndexPaths
sortDescriptors


// **NSUserDefaultsController**
hasUnappliedChanges
values

    So, find the one on the list you want, look in the docs for that controller class, and you’ll find its definition. If it’s not there, it’s probably defined in the docs for its superclass (likely NSObjectController).

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