+ (void)initialize
{
    [super initialize];

    [self exposeBinding:@"date"];
    [self exposeBinding:@"minDate"];
    [self exposeBinding:@"maxDate"];
}
- (void)awakeFromNib
{
    [super awakeFromNib];

    // …
    [self establishBindings];

}

- (void)establishBindings
{
    NSArray *keys = [NSArray arrayWithObjects:@"date", @"minDate", @"maxDate", nil];

    NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys:
                              [NSNumber numberWithBool:YES], NSContinuouslyUpdatesValueBindingOption,
                              [NSNumber numberWithBool:YES], NSConditionallySetsEnabledBindingOption,
                              [NSNumber numberWithBool:YES], NSValidatesImmediatelyBindingOption,
                              [NSNumber numberWithBool:NO], NSRaisesForNotApplicableKeysBindingOption,
                              [NSNumber numberWithBool:NO], NSAllowsEditingMultipleValuesSelectionBindingOption,
                              nil];

    // This code allows creation of bindings via interface builder without actual
    // support for custom bindings in IB. I hijack the 'user defined runtime attributes'
    // and define binding keypath there, and I use an IBOutlet to define a binding
    // target.
    for(NSString *key in keys)
    {
        id bindingTarget = [self valueForKey:[key stringByAppendingString:@"BindingTarget"]];;
        id bindingKeyPath = [self valueForKey:[key stringByAppendingString:@"BindingKeyPath"]];;
        if (!bindingTarget || !bindingKeyPath)
            continue;

        [bindingTarget valueForKeyPath:bindingKeyPath];

        [self bind:key
          toObject:[self valueForKey:[key stringByAppendingString:@"BindingTarget"]]
       withKeyPath:[self valueForKey:[key stringByAppendingString:@"BindingKeyPath"]]
           options:options];

    }
}

// one of the custom setters
- (void)setDate:(NSDate *)date
{
    if(_date == date)
        return;

    [self willChangeValueForKey:@"date"];
    [date retain];
    [_date release];
    _date = date;
    [self didChangeValueForKey:@"date"];

    NSDictionary * infoForBinding = [self infoForBinding:@"date"];
    if(infoForBinding && [infoForBinding objectForKey:NSObservedObjectKey])
    {
        id observedObject = [infoForBinding objectForKey:NSObservedObjectKey];
        NSString * observedKeyPath = [infoForBinding objectForKey:NSObservedKeyPathKey];

        if([[observedObject valueForKeyPath:observedKeyPath] isEqual:NSMultipleValuesMarker])
        {
            // This is needed because, when performing multiple selection,
            // we get called with setDate:nil. Then we blindly apply this to
            // the entire selection.
            // For our needs, it's enough to block applying values to multiple
            // selection. But it's not a correct solution.

            // FIXME: we currently block editing of multiple selection.
            NSLog(@"Not applying value for keypath %@ to %@; currently multiple items are selected", observedKeyPath, observedObject);
        }
        else
        {
            [observedObject setValue:date forKeyPath:observedKeyPath];
        }
    }

    if(self.date)
        if(self.formatter)
            [self setTitle:[self.formatter stringForObjectValue:date]];
        else
            [self setTitle:[date description]];
    else
        [self setTitle:@"-"];
}