更改rootviewcontroller导致内存泄漏

Question

我在问自己之前检查了所有的问题，但是没有一个能适合我。

当我在第一次运行时打开我的应用程序时，我调用了FirstViewController（它包含两个按钮：注册或登录）。如果用户选择注册，我会带上RegisterViewController（它包含一个按钮，让用户登录以防他改变主意）。最后一个LoginViewController（还包含一个打开注册屏幕的按钮）

FirstViewController中两个按钮的代码

- (IBAction)signupPressed:(id)sender {
    AppDelegate *app = (AppDelegate*) [UIApplication sharedApplication].delegate;
    app.window.rootViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"RegisterViewController"];
}

- (IBAction)loginPressed:(id)sender {
    AppDelegate *app = (AppDelegate*) [UIApplication sharedApplication].delegate;
    app.window.rootViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"LoginViewController"];
}

通往LoginViewController的RegisterViewController按钮的代码（我尝试过其中一个解决方案，但失败了）

- (IBAction)loginPressed:(id)sender {
    AppDelegate *app = (AppDelegate*) [UIApplication sharedApplication].delegate;


    UIViewController *previousRootViewController = app.window.rootViewController;

    app.window.rootViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"LoginViewController"];

    // Nasty hack to fix http://stackoverflow.com/questions/26763020/leaking-views-when-changing-rootviewcontroller-inside-transitionwithview
    // The presenting view controllers view doesn't get removed from the window as its currently transistioning and presenting a view controller
    for (UIView *subview in app.window.subviews) {
        if ([subview isKindOfClass:NSClassFromString(@"UITransitionView")]) {
            [subview removeFromSuperview];
        }
    }
    // Allow the view controller to be deallocated
    [previousRootViewController dismissViewControllerAnimated:NO completion:^{
        // Remove the root view in case its still showing
        [previousRootViewController.view removeFromSuperview];
    }];
}

LoginViewController：指向RegisterViewController的代码。

- (IBAction)signupPressed:(id)sender {
    AppDelegate *app = (AppDelegate*) [UIApplication sharedApplication].delegate;
    app.window.rootViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"RegisterViewController"];
}

上面提到的代码总是创建一个新实例，我使用Instruments跟踪了应用程序。

单击FirstViewController上的注册，创建RegisterViewController的第一个实例

单击登录按钮（RegisterViewController），然后单击注册按钮（LoginViewController）

这两个实例都是由UIKit发布的

有没有机会管理这些泄漏？