self.navigationController是nil第二次加载ViewController

Question

I have a delegate/handler that i have implemented on my UIViewControllers to handle timeouts to the a remote webservice. When a request is made to my webservice, and a timeout http code is returned, the delegate is called and performs the following:

UINavigationController *navController = self.navigationController;

if (navController) {
    [navController popToRootViewControllerAnimated:YES];
} else {
    NSLog(@"navController is null/nil");
}

If I do the following steps, navController is instantiated correctly and the popToRootViewController action occurs.

1. Authenticate my app with the webservice on a Login ViewController
2. Auto trigger a segue to a CustomMenuViewController
3. Wait for the webservice to timeout remotely
4. Click to trigger a segue to CustomSubMenuViewController

Now, if i do the following steps, the else clause in the above code block is triggered because for some reasons navController isn't being set correctly:

1. Authenticate my app with the webservice on a CustomLoginViewController
2. Auto segue to a CustomMenuViewController
3. Immediately click to trigger a segue to CustomSubMenuViewController
4. Click back button to trigger a pop
5. Wait for the webservice to timeout remotely
6. Click to trigger a segue to the same CustomSubMenuViewController

My question is: why when i load a ViewController for the second time, does self.navigationController return null?

The call stack in the above example should look like this: NavigationController -> CustomLoginViewController -> CustomMenuViewController -> CustomSubMenuViewController

Thanks

UPDATE: Still haven't made any progress on this issue!

Answer 1

嘿，这可能听起来很基本，但是，你是否正确分配了Navbar对象，也许你可以尝试将其属性设置为强大。也许这样它就会在时间之前被释放。

Answer 2

I think you might have already resolved this but i encountered the exact same thing. And I think we might be doing the exact same thing like using facebook for login. Anyway for some one else in the future this might be useful. The issue that i had that i was re allocating the UINavigationController again when coming back from background on a failure condition.

So what you can do is try to put a breakpoint around the place where you initialise your rootViewController for the UiNavigationController.

 [[UINavigationController alloc]
        initWithRootViewController:viewController]; and make sure that you do re-initailise your UINavigationController if you have already done it.