binding NSTextField to NSNumber

Question

I\'m trying to use an NSTextField for integer user input. The text field is bound to an NSNumber property and in the setter method I cleanup the input value (make sure it\'s

Answer 1

There’s an important comment on Peter Hosey’s excellent answer that I’d like to bring up to the top level (because I missed it on my first pass).

If you want to validate / modify the NSTextField each time a character is entered, rather than only when the user submits the field, then you can’t get what you want from bindings alone. You need to assign a delegate to the text field, and then implement - (void)controlTextDidChange:(NSNotification *)aNotification in the delegate. This will get called every time the text changes. If you want, you can call the value validator in controlTextDidChange.

For example:

- (void)controlTextDidChange:(NSNotification *)aNotification
{
    NSError *outError;
    NSControl *textField = [aNotification object];
    NSString *myText = [textField stringValue];

    // myObject is the model object that owns the text in question
    // the validator can modify myText by reference
    [myObject validateValue:&myText error:&outError]];

    // update the NSNextField with the validated text
    [postingObject setStringValue:myText];
}