当多个属性更改时执行操作

我目前的执行情况如下:

@property (readonly) NSNumber *meta;

+ (NSSet *)keyPathsForValuesAffectingMeta
{
  return [NSSet setWithObjects:@"x", @"y", @"z", nil];
}

- (void)awakeFromNib
{
  [self addObserver:self forKeyPath:@"meta" options:0 context:NULL];
}

- (NSNumber *)meta
{
  BOOL meta = x || y || z;
  return [NSNumber numberWithBool:meta];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
  BOOL meta = [[self meta] boolValue];
  if (meta != _flags.meta) {
    if (meta) {
      [self showSomeStuff];
    }
    else {
      [self hideSomeStuff];
    }

  _flags.meta = meta;
  }
}

它是有效的,但我希望有一个更容易和更好的解决方案,像这样的事情,我目前正在忽视。打我!