Cocoa: Stopping the field editor from auto-completing on space key

I have a custom view with several NSTextField controls for which I want to supply custom auto-completions and I have successfully implemented all that using the NSTextFieldDelegate Protocol. The auto-completions are full names or place names, depending on which text field is being edited.

The issue is that the auto-completions almost always contain a space character and so if the user is typing something that matches a suggestion, but doesn't want to accept that suggestion, the field editor will accept the suggestion when user presses the space key. I want the field editor to accept the suggestion using the tab key only.

I understand that this will involve subclassing NSTextView to provide a custom field editor, and this is documented by Apple as being the acceptable way, however it's not clear to me what methods I need to override and what the overridden methods need to do, in order to get me what I want.

Can anyone suggest how this is achieved?

I admit that I'd been fumbling with this question for quite some time earlier, before I discovered an acceptable answer via Google-fu. The magic code, blatantly stolen from the original answerer:

@interface MLFieldEditor : NSTextView @end

@implementation MLFieldEditor


-  (void)insertCompletion:(NSString *)word forPartialWordRange:(NSRange)charRange movement:(NSInteger)movement isFinal:(BOOL)flag {
    // suppress completion if user types a space
    if (movement == NSRightTextMovement) return;

    // show full replacements
    if (charRange.location != 0) {
        charRange.length += charRange.location;
        charRange.location = 0;
    }

    [super insertCompletion:word forPartialWordRange:charRange movement:movement isFinal:flag];

    if (movement == NSReturnTextMovement)
    {
        [[NSNotificationCenter defaultCenter] postNotificationName:MLSearchFieldAutocompleted object:self userInfo:nil];
    } }

@end

(Additional reference)