Cocoa-Bindings : Bind NSComboBox selection to a field in NSObjectController

Question

Hello,

in my application I have a NSObjectController bound to all controls on the user interface. This works fine so far. The only problem I have is binding the selection of an NSComboBox to the same ObjectController. As far as I found out today the value of a ComboBox is always a string so the field in the Class of the OBjectController is also an NSString.Sounds easy for me but doesn't work.

I always get an "... class is not key value coding-compliant for the key ..."

The items in the ComboBox itself come from an other Controller, a NSArrayController. But that part works fine. All the items from the Array are items in the ComboBox. The Problem I have is getting the selection into to ObjectController.

Answer 1

It's just saying that whatever data-model object that NSObjectController is using does't have an appropriate key method for that value.

From looking at the Cocoa Bindings Reference documentation, the value binding should be set to a key in your NSObjectController that corresponds to a key-value-coding compliant key in its model.

Example:

NSObjectController mode is Class, Class Name is foo. Then you bind foo's key of comboSelection to the NSComboBox's value. What the exception is saying is that the Foo class doesn't have a method called comboSelection:

- (NSString*)comboSelection;
- (void)setComboSelection:(NSString*)inSelection;

In the case of using a NSMutableDictionary as the NSObjectController's class, it's much easier, since the dictionary can hold arbitrary keys.

If you're using CoreData (mode = Entity), then your CoreData entity must contain the appropriate property.