Customising object removal from NSArrayController

gistfile1.m

- (void)willRemoveObject:(id)object;
{
    // Put your removal handling code here
}

- (void)removeObjects:(NSArray *)objects
{
    // -removeObject: calls this method internally.
    // Iterate the objects, reporting each one
    
    for (id anObject in objects)
    {
        [self willRemoveObject:anObject];
    }
    
    [super removeObjects:objects];
}

- (void)removeObjectAtArrangedObjectIndex:(NSUInteger)index
{
    // -removeObjectsAtArrangedObjectIndexes: calls this repeatedly
    
    id object = [[self arrangedObjects] objectAtIndex:index];
    [self willRemoveObject:object];
    
    [super removeObjectAtArrangedObjectIndex:index];
}