Can't add self as subview

最近在iOS的项目中出现了Can't add self as subview 的crash，日志信息如下

从日志上来看崩溃是在main函数，定位不到具体的地方。

像这种crash，一般最简单地情况是：

[self.view addSubview:self.view];

这种确实会直接导致崩溃，但不是引起原因。

另一种错误原因是说一次push了两次，动画被打断后引起的crash。

对push的UIViewController来进行进行控制。

另一种方法：

创建一个分类，拦截控制器入栈\出栈的方法调用，通过安全的方式，确保当有控制器正在进行入栈\出栈操作时，没有其他入栈\出栈操作。

此分类用到运行时 (Runtime) 的方法交换Method Swizzling，因此只需要复制下面的代码到自己的项目中，此 bug 就不复存在了。

#import  "UINavigationController+Consistent.h"

#import  <objc/runtime.h>

/// This char is used to add storage for the is PushingViewController property.

static char const *const ObjectTagKey ="ObjectTag";

@interfaceUINavigationController ()

@property(readwrite, getter= isViewTransitionInProgress) BOOL viewTransitionInProgress;

@end

@implementation  UINavigationController (Consistent)

- (void)setViewTransitionInProgress:(BOOL)property {

            NSNumber *number = [NSNumber numberWithBool:property];

           objc_setAssociatedObject(self, ObjectTagKey, number , OBJC_ASSOCIATION_RETAIN);

}

- (BOOL)isViewTransitionInProgress {

          NSNumber *number = objc_getAssociatedObject(self, ObjectTagKey);

        return   [number boolValue];

}

#pragma mark - Intercept Pop, Push, PopToRootVC

/// @name Intercept Pop, Push, PopToRootVC

- (NSArray *)safePopToRootViewControllerAnimated:(BOOL)animated {

     if(self.viewTransitionInProgress)   return    nil;

     if(animated) {

              self.viewTransitionInProgress =YES;

       }

//-- This is not a recursion, due to method swizzling the call below calls the originalmethod.

      return  [self  safePopToRootViewControllerAnimated:animated];

}

- (NSArray *)safePopToViewController:(UIViewController *)viewController animated:(BOOL)animated {

         if(self.viewTransitionInProgress)  return  nil;     

       if(animated) {

                  self.viewTransitionInProgress = YES;

      }

//-- This is not a recursion, due to method swizzling the call below calls the originalmethod.

      return [self   safePopToViewController:viewController animated:animated];

}

- (UIViewController *)safePopViewControllerAnimated:(BOOL)animated {

      if(self.viewTransitionInProgress)     return    nil; 

     if(animated) {

              self.viewTransitionInProgress =YES;

     }

//-- This is not a recursion, due to method swizzling the call below calls the originalmethod.

      return  [self  safePopViewControllerAnimated:animated];

}

- (void)safePushViewController:(UIViewController *)viewController animated:(BOOL)animated {

         self.delegate =self;

//-- If we are already pushing a view controller, we dont push another one.

        if(self.isViewTransitionInProgress ==NO) {

//-- This is not a recursion, due to method swizzling the call below calls the originalmethod.

     [self   safePushViewController:viewController animated:animated];

     if(animated) {

     self.viewTransitionInProgress =YES;

     }

   }

}

// This is confirmed to be App Store safe.

// If you feel uncomfortable to use Private API, you could also use the delegate method navigationController:didShowViewController:animated:.

- (void)safeDidShowViewController:(UIViewController *)viewController animated:(BOOL)animated {

//-- This is not a recursion. Due to method swizzling this is calling the original method.

     [self  safeDidShowViewController:viewController animated:animated]; 

    self.viewTransitionInProgress =NO;

}

// If the user doesnt complete the swipe-to-go-back gesture, we need to intercept it and set the flag to NO again.

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {

   id tc = navigationController.topViewController.transitionCoordinator;

   [tc notifyWhenInteractionEndsUsingBlock:^(id context) {

               self.viewTransitionInProgress =NO;

              //--Reenable swipe back gesture.

             self.interactivePopGestureRecognizer.delegate = (id)viewController;

            [self.interactivePopGestureRecognizer setEnabled:YES];

}];

//-- Method swizzling wont work in the case of a delegate so: 

  //-- forward this method to the original delegate if there is one different than ourselves.

      if(navigationController.delegate !=self) {

      [navigationController.delegate navigationController:navigationController

               willShowViewController:viewController

                animated:animated];

        }

}

+ (void)load {

//-- Exchange the original implementation with our custom one.

method_exchangeImplementations(class_getInstanceMethod(self,@selector(pushViewController:animated:)),class_getInstanceMethod(self,@selector(safePushViewController:animated:)));

method_exchangeImplementations(class_getInstanceMethod(self,@selector(didShowViewController:animated:)),class_getInstanceMethod(self,@selector(safeDidShowViewController:animated:)));

method_exchangeImplementations(class_getInstanceMethod(self,@selector(popViewControllerAnimated:)),class_getInstanceMethod(self,@selector(safePopViewControllerAnimated:)));

method_exchangeImplementations(class_getInstanceMethod(self,@selector(popToRootViewControllerAnimated:)),class_getInstanceMethod(self,@selector(safePopToRootViewControllerAnimated:)));

method_exchangeImplementations(class_getInstanceMethod(self,@selector(popToViewController:animated:)),class_getInstanceMethod(self,@selector(safePopToViewController:animated:)));

}

@end

参考文件：

Can't add self as subview

Can't Add Self as Subview 崩溃解决办法