typedef NS_ENUM(NSInteger, UINavigationControllerOperation) {
    UINavigationControllerOperationNone,
    UINavigationControllerOperationPush,
    UINavigationControllerOperationPop,
};

一.属性

//在这个导航栈最顶层的controller
@property(nullable, nonatomic,readonly,strong) UIViewController *topViewController; // The top view controller on the stack.
//当前显示的VC
@property(nullable, nonatomic,readonly,strong) UIViewController *visibleViewController; // Return modal view controller if it exists. Otherwise the top view controller.
//当前所有在栈里面的VC(栈是被调用出来的页面集合吗？）
@property(nonatomic,copy) NSArray<__kindof UIViewController *> *viewControllers; // The current view controller stack.
//隐藏导航栏
@property(nonatomic,getter=isNavigationBarHidden) BOOL navigationBarHidden;

//导航条，会有很多自己的属性和方法
@property(nonatomic,readonly) UINavigationBar *navigationBar; // The navigation bar managed by the controller. Pushing, popping or setting navigation items on a managed navigation bar is not supported.
//隐藏工具栏
@property(nonatomic,getter=isToolbarHidden) BOOL toolbarHidden NS_AVAILABLE_IOS(3_0) __TVOS_PROHIBITED; // Defaults to YES, i.e. hidden.
//工具栏，就是微信页面下面的那一栏
@property(null_resettable,nonatomic,readonly) UIToolbar *toolbar NS_AVAILABLE_IOS(3_0) __TVOS_PROHIBITED; // For use when presenting an action sheet.
//代理
@property(nullable, nonatomic, weak) id<UINavigationControllerDelegate> delegate;

//左划返回手势：
苹果一直都在人机交互中尽力做到极致，在iOS7中，新增加了一个小小的功能，也就是这个api：self.navigationController.interactivePopGestureRecognizer.enabled = YES;
这个api功能就是在NavigationController堆栈内的UIViewController可以支持右滑手势，也就是不用点击右上角的返回按钮，轻轻在屏幕左边一
滑，屏幕就会返回，随着ios设备屏幕的增大，这个小功能让手指短，拇指大和手残人士看到了福音。
这个功能是好，但是经常我们会有需求定制返回按钮，如果手动定制了返回按钮，这个功能将会失效，也就是自定义了navigationItem的leftBarButtonItem，那么这个手势就会失效。解决方法找到两种 
 1.重新设置手势的delegate
 self.navigationController.interactivePopGestureRecognizer.delegate = (id)self;
 2.当然你也可以自己响应这个手势的事件
 [self.navigationController.interactivePopGestureRecognizer addTarget:self action:@selector(handleGesture:)];
有更多方法以后继续补充，这里可以根据自己需要进行选择，如果只是简单定制了返回按钮，第一种最简单，一句代码搞定。
@property(nullable, nonatomic, readonly) UIGestureRecognizer *interactivePopGestureRecognizer NS_AVAILABLE_IOS(7_0) __TVOS_PROHIBITED;

/// When the keyboard appears, the navigation controller's navigationBar toolbar will be hidden. The bars will remain hidden when the keyboard dismisses, but a tap in the content area will show them.
//当键盘弹出时隐藏导航栏，但是键盘消失时不会自动出现，需要主动点击导航栏部分时才会从新出现（现在在我手机上不行？不能正常出现，一直没了)
@property (nonatomic, readwrite, assign) BOOL hidesBarsWhenKeyboardAppears NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
//在导航栏上上下滑动实现导航栏的消失出现，常用于tableView,上滑隐藏导航栏，下滑显示，带动画效果
/// When the user swipes, the navigation controller's navigationBar & toolbar will be hidden (on a swipe up) or shown (on a swipe down). The toolbar only participates if it has items.
@property (nonatomic, readwrite, assign) BOOL hidesBarsOnSwipe NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
/// The gesture recognizer that triggers if the bars will hide or show due to a swipe. Do not change the delegate or attempt to replace this gesture by overriding this method.
//滑动消失导航栏的手势
@property (nonatomic, readonly, strong) UIPanGestureRecognizer *barHideOnSwipeGestureRecognizer NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
//横屏的时候隐藏导航栏
/// When the UINavigationController's vertical size class is compact, hide the UINavigationBar and UIToolbar. Unhandled taps in the regions that would normally be occupied by these bars will reveal the bars.
@property (nonatomic, readwrite, assign) BOOL hidesBarsWhenVerticallyCompact NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
//单击(tap)非导航栏处，隐藏或显示导航栏
/// When the user taps, the navigation controller's navigationBar & toolbar will be hidden or shown, depending on the hidden state of the navigationBar. The toolbar will only be shown if it has items to display.
@property (nonatomic, readwrite, assign) BOOL hidesBarsOnTap NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
//单击导航栏消失隐藏手势
/// The gesture recognizer used to recognize if the bars will hide or show due to a tap in content. Do not change the delegate or attempt to replace this gesture by overriding this method.
@property (nonatomic, readonly, assign) UITapGestureRecognizer *barHideOnTapGestureRecognizer NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;

二.方法