我有masterViewController和detailViewController。Masterview推送detailView。回到masteViewController时，我想更新foo值。但我只从nslog中得到NULL。导航返回时如何将parenteViewContrller.foo值设置为@"bar"？masterViewController.hNSString*foo;-(void)setFoo:(NSString*)fooValue@property(nonatomic,retain)NSString*foo;masterViewController.m@synthe