tableBar 嵌套NavGationController 无法使用手势返回的问题

@property (weak,nonatomic) id<UIGestureRecognizerDelegate>navdel;
    //写在ViewWillAppear
    NSArray * VCs = self.navigationController.viewControllers;
    if (VCs.count && self != VCs[0]) {
        self.navigationController.interactivePopGestureRecognizer.delegate=self;
    }else if (VCs.count && self == VCs[0])
    {
        self.navigationController.interactivePopGestureRecognizer.delegate=self.navdel;
    }
    //写在viewDidLoad
    self.navdel=self.navigationController.interactivePopGestureRecognizer.delegate;