Ios ***由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因是：“试图弹出到不存在的视图控制器。”

我有一个没有被捕获的异常，即使是在处理异常@try{}@catch{}，这可能是非常简单的事情，但我现在看不到它。异常显示“试图弹出到不存在的视图控制器”。我相信某个参数是pass nil，但我没有看到它：

-(void) theProblemMethod
{

    dispatch_async(dispatch_get_main_queue(), ^{
        @try {
                [[self topViewController] dismissViewControllerAnimated:YES completion: ^{

                     UIViewController * rootViewControler = nil;
                    if ((rootViewControler = (UIViewController *) [UIApplication sharedApplication].keyWindow.rootViewController))
                     {
                         if([self topViewController])
                             [(UINavigationController *)[self topViewController].navigationController popToViewController:rootViewControler animated:YES];
                         if ((rootViewControler = (UIViewController *) [[[[UIApplication sharedApplication] delegate] window] rootViewController].presentedViewController)) {
                             [rootViewControler dismissViewControllerAnimated:YES completion:
                              ^{
                                  //do something here
                              }];
                         }
                     }
                 }];

        } @catch (NSException *exception) {
            NSLog(@"There is a problem at [myClass theProblemMethod]  Exception: %@, reason: %@",  [exception name], [exception reason]);
        } @finally {}
     });
}

---

有人看到问题吗？

当弹出视图控制器为零，或者弹出视图控制器不在导航视图控制器堆栈中时，会发生此错误。在弹出前检查两个

UIViewController *poppedVC = ...
UINavigationController *nc = ...
if (poppedVC && [nc.viewControllers containsObject:poppedVC]) {
    [nc popViewControllerAnimated:poppedVC];
}

我发现了问题！我刚刚发现问题的症结在于：

[(UINavigationController *)[self topViewController].navigationController popToViewController:rootViewControler animated:YES];

我的代码试图在关闭topViewController查看其父级后访问属性navigationController

解决方案是在@try:

最后：

 -(void) theProblemMethod
    {

        dispatch_async(dispatch_get_main_queue(), ^{
            @try {
                    UINavigationController * aNavigationController = (UINavigationController *)[[self topViewController] navigationController];
                    [[self topViewController] dismissViewControllerAnimated:YES completion: ^{

                         UIViewController * rootViewControler = nil;
                        if ((rootViewControler = (UIViewController *) [UIApplication sharedApplication].keyWindow.rootViewController))
                         {
                                 [(UINavigationController *)[self topViewController].navigationController popToViewController:rootViewControler animated:YES];
                             if ((rootViewControler = (UIViewController *) [[[[UIApplication sharedApplication] delegate] window] rootViewController].presentedViewController)) {
                                 [rootViewControler dismissViewControllerAnimated:YES completion:
                                  ^{
                                      //do something here
                                  }];
                             }
                         }
                     }];

            } @catch (NSException *exception) {
                NSLog(@"There is a problem at [myClass theProblemMethod]  Exception: %@, reason: %@",  [exception name], [exception reason]);
            } @finally {}
         });
    }

---

基本上，我是在移除A的同时尝试调用它的子A.child，在A被移除之后

我尝试了此解决方案，但没有成功，因为if条件不适用于此情况，因为rootViewController不是topViewController.navigationController的子项。

 -(void) theProblemMethod
    {

        dispatch_async(dispatch_get_main_queue(), ^{
            @try {
                    UINavigationController * aNavigationController = (UINavigationController *)[[self topViewController] navigationController];
                    [[self topViewController] dismissViewControllerAnimated:YES completion: ^{

                         UIViewController * rootViewControler = nil;
                        if ((rootViewControler = (UIViewController *) [UIApplication sharedApplication].keyWindow.rootViewController))
                         {
                                 [(UINavigationController *)[self topViewController].navigationController popToViewController:rootViewControler animated:YES];
                             if ((rootViewControler = (UIViewController *) [[[[UIApplication sharedApplication] delegate] window] rootViewController].presentedViewController)) {
                                 [rootViewControler dismissViewControllerAnimated:YES completion:
                                  ^{
                                      //do something here
                                  }];
                             }
                         }
                     }];

            } @catch (NSException *exception) {
                NSLog(@"There is a problem at [myClass theProblemMethod]  Exception: %@, reason: %@",  [exception name], [exception reason]);
            } @finally {}
         });
    }