NSUndoManager - Undo Button not showing up

Question

I have a Document which has a meeting. When I initialize the meeting, I set the undoManager to point to the Document's undoManager. Likewise, my meeting has attendees (list of Person). Each Person object simply points back to my meeting's undoManager which in turn is just a pointer to the Document.

My undo for adding and removing attendees to the meeting was working until I started observing the key values for attributes of the person.

Any ideas on what I am doing wrong? When I add and remove an attendee, the undo button does not activate. Likewise, when I make a change to the person's name/rate, the undo button does not show up.

Document.m

- (id)init
{
    self = [super init];
    if (self) {
        self.meeting = [[Meeting alloc] init];
        self.meeting.undoManager = self.undoManager;

meeting.h ---

@property (nonatomic, retain) NSUndoManager *undoManager;

meeting.m

- (void)changeKeyPath:(NSString *)keyPath
         ofObject:(id)obj
          toValue:(id)newValue {
// setValue:forKeyPath: will cause the key-value observing method
// to be called, which takes care of the undo stuff
[obj setValue:newValue forKeyPath:keyPath];
}

- (void)observeValueForKeyPath:(NSString *)keyPath
                  ofObject:(id)object
                    change:(NSDictionary *)change
                   context:(void *)context {
    id oldValue = [change objectForKey:NSKeyValueChangeOldKey]; 
    // NSNull objects are used to represent nil in a dictionary
    if (oldValue == [NSNull null]) {
        oldValue = nil;
}

    [[self.undoManager prepareWithInvocationTarget:self] changeKeyPath:keyPath
                                                          ofObject:object
                                                           toValue:oldValue];
   // Notify the undoManager
   self.undoManager.actionName = @"Edit";

}

- (void)startObservingPerson:(Person *)person {
    // TODO: Understand if I need something for context
    [person addObserver:self
         forKeyPath:@"name"
            options:NSKeyValueObservingOptionOld
            context:nil];

    [person addObserver:self
         forKeyPath:@"rate"
            options:NSKeyValueObservingOptionOld
            context:nil];

}

- (void)stopObservingPerson:(Person *)person    {
    [person removeObserver:self forKeyPath:@"name"];
    [person removeObserver:self forKeyPath:@"rate"];
}

-(void) insertObject:(id *)object inAttendeeListAtIndex:(NSUInteger)index {

    [(Person *)object setMeeting:self];
    // Enable undo capabilities for edits to the name/rate
    [self startObservingPerson:(Person *)object];
    // insert the object / person
    [self.attendeeList insertObject:(Person *)object atIndex:index];

    //
    // configure the undo for the insert
    [[self.undoManager prepareWithInvocationTarget:self] removeObjectFromAttendeeListAtIndex:(NSUInteger) index];

    undoManager.actionName = @"Insert Person";

}

-(void) removeObjectFromAttendeeListAtIndex:(NSUInteger)index {
    Person *deletedPerson = [self.attendeeList objectAtIndex:index];
    // housecleaning before removing the person
    [self stopObservingPerson:(Person *)deletedPerson];

    // remove the object / person
    [self.attendeeList removeObjectAtIndex:index];

    // configure the undo
    [[self.undoManager prepareWithInvocationTarget:self] insertObject:(id *)deletedPerson inAttendeeListAtIndex:index];

    // Notify the undoManager
    undoManager.actionName = @"Remove Person";

}

Answer 1

I found the answer to my problem. I initialize meetings one of two ways. New documents and through archived documents. When I was loading from the archive, I wasn't assigning the undoManager so it was null and nothing was happendi