往UISegmentedControl上添加几个控制器

 #import "RootViewController.h"
 #import "LoginViewController.h"
 #import "RegistViewController.h"
 #import "PasswardViewController.h"
 #import "RootView.h"

 @interface RootViewController ()
 @property (nonatomic, strong) RootView *rootView;
 @property (nonatomic, strong) LoginViewController *loginVC;
 @property (nonatomic, strong) RegistViewController *registVC;
 @property (nonatomic, strong) PasswardViewController *passwardVC;

 @end

 @implementation RootViewController

 - (void)loadView {
     self.rootView = [[RootView alloc] initWithFrame:[UIScreen mainScreen].bounds];
     self.view = self.rootView;

 }

 - (void)viewDidLoad {
     [super viewDidLoad];

     // 初始化视图控制器
     self.loginVC = [[LoginViewController alloc] init];
     self.registVC = [[RegistViewController alloc] init];
     self.passwardVC = [[PasswardViewController alloc] init];

     // segment添加一个事件
     [self.rootView.segment addTarget:self action:@selector(click:) forControlEvents:UIControlEventValueChanged];

 }

 // 实现点击事件
 - (void)click:(UISegmentedControl *)sender {

     switch (sender.selectedSegmentIndex) {
         case :
             // 移除父视图中最上面的子视图
             [[self.rootView.subviews objectAtIndex:] removeFromSuperview];

             // 添加新视图
             [self.rootView addSubview:self.loginVC.view];

             // 把分段选择器显示在最外层
             [self.rootView bringSubviewToFront:self.rootView.segment];
             break;

         case :
             // 移除父视图中最上面的子视图
             [[self.rootView.subviews objectAtIndex:] removeFromSuperview];

             // 添加新视图
             [self.rootView addSubview:self.registVC.view];

             // 把分段选择器显示在最外层
             [self.rootView bringSubviewToFront:self.rootView.segment];
             break;

         case :
             // 移除父视图中最上面的子视图
             [[self.rootView.subviews objectAtIndex:] removeFromSuperview];

             // 添加新视图
             [self.rootView addSubview:self.passwardVC.view];

             // 把分段选择器显示在最外层
             [self.rootView bringSubviewToFront:self.rootView.segment];
             break;

         default:
             break;
     }
 }
 @end