iOS 删除前面一切跳转，跳转到根视图！

一些场景需要把一切跳转干掉，回到根视图！（一位大佬写的，俺只是搬运工）

• 思路1：root有3种可能 1.控制器 2拥有导航栏的控制器 3是tabBar控制器

• 思路2：首先理解presentedViewController presentingViewController visibleViewController这3个属性

• 思路3：我们可以拿到root所对应的控制器跟当前的最上层进行比较，如果不一样，说明显示层不是root，不是root那我们则需要把前面一长串跳转干掉，如何完美的干掉这一长串呢？我们知道dismiss这个方法有个代码块，这就说明了该方法存在延迟性，如果一层一层的dismiss那么是有可能出问题的。

• 思路3：既然不能一层一层的进行dismiss那么我们可以换一种思路，拿到当前显示层后一层一层往下找，直到该控制器没有下一层时我们直接拿该控制器进行dismiss就可以了，nav就使用popToRoot！

  #import 
  #import 
  typedef NS_ENUM(NSUInteger, AnimationType) {
      AnimationTypeBottom,
      AnimationTypeLeft,
  };
  
  
  @interface JumpVCManager : NSObject
  @property (nonatomic,strong) UIViewController* rootVC;
  + (instancetype)shareInstance;
   - (void)backToRootVCAnimation:(AnimationType)type;
  - (void)backToRootVC;
  - (UIViewController *)visibleVC;
  @end
  
  
  #import "JumpVCManager.h"
  @interface JumpVCManager()
  @property (nonatomic) BOOL isJumping;// 是否正在跳转
  @end
  @implementation JumpVCManager
  + (instancetype)shareInstance{
  static JumpVCManager *_shareInstance = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
      _shareInstance = [[self alloc] init];
  });
  return _shareInstance;
  }
  
  - (UIViewController *)rootVC{
     UIViewController *rootViewcontroller = [[[[UIApplication  sharedApplication] delegate] window] rootViewController];
     UIViewController *rootVC = rootViewcontroller;
     if ([rootViewcontroller isKindOfClass:[UITabBarController class]]) {
        UITabBarController *tabVC =  (UITabBarController*)rootViewcontroller;
        if ([tabVC.selectedViewController isKindOfClass:[UINavigationController class]]) {
            rootVC = [(UINavigationController*)(tabVC.selectedViewController) viewControllers][0];
        } else {
            rootVC = tabVC.selectedViewController;
        }
    } else if ([rootViewcontroller isKindOfClass:[UINavigationController class]]) {
        UINavigationController *nav =  (UINavigationController *)rootViewcontroller;
        rootVC = nav.viewControllers[0];
    }
    return rootVC;
  }
  
  
  - (void)backToRootVCAnimation:(AnimationType)type{
     [self addAnimationWithType:type];
     [self backToRootVC];
  }
  
  - (void)addAnimationWithType:(AnimationType)type{
      CATransition *animation = [CATransition animation];
      //动画时间
      animation.duration = 0.25f;
      //过滤效果
      animation.type = kCATransitionReveal;
      //动画执行完毕时是否被移除
      animation.removedOnCompletion = YES;
      animation.subtype = kCATransitionFromBottom;
      if (type == AnimationTypeLeft) {
          animation.subtype = kCATransitionFromLeft;
      }
      [[UIApplication sharedApplication].keyWindow.layer addAnimation:animation forKey:nil];
  }
  
  - (void)backToRootVC{
      if (self.isJumping == NO) {
          self.isJumping = YES;
           NSLog(@"start");
          [self backToRootViewController];
      }
  }
  
  - (void)backToRootViewController{
      NSLog(@"bbbbbbbbbbbbbbb");
      UIViewController* vc = [self visibleVC];
      if ([vc isEqual:self.rootVC]) {
          NSLog(@"end");
          self.isJumping = NO;
          return;
      }
      if (vc.presentingViewController) {
          while (vc.presentingViewController) {
              vc = vc.presentingViewController;
          }
          [vc dismissViewControllerAnimated:NO completion:^{
          [self backToRootViewController];
          }];
      } else{
          [vc.navigationController popToRootViewControllerAnimated:NO];
          [self backToRootViewController];
      }
  }
  
  
  - (UIViewController *)visibleVC{
      UIViewController *rootViewController =[[[[UIApplication sharedApplication] delegate] window] rootViewController];
      return [JumpVCManager                getVisibleViewControllerFrom:rootViewController];
  }
  
  + (UIViewController *) getVisibleViewControllerFrom:(UIViewController *) vc {
     if ([vc isKindOfClass:[UINavigationController class]]) {
          return [JumpVCManager getVisibleViewControllerFrom:[((UINavigationController *) vc) visibleViewController]];
      } else if ([vc isKindOfClass:[UITabBarController class]]) {
          return [JumpVCManager getVisibleViewControllerFrom:[((UITabBarController *) vc) selectedViewController]];
      } else {
          if (vc.presentedViewController) {
              return [JumpVCManager getVisibleViewControllerFrom:vc.presentedViewController];
          } else {
              return vc;
          }
      }
  }
  
  @end