@interface MyView : UIView

@property (strong, nonatomic) UIButton *myBtn;

@end

#import "MyView.h" 

@implementation MyView
//view的初始化方法
- (id)initWithFrame:(CGRect)frame
{
  self = [super initWithFrame:frame];
  if (self)
  {  //初始化按钮
    _myBtn = [[UIButton alloc] initWithFrame:CGRectMake(140, 100, 100, 50)];
    _myBtn.backgroundColor = [UIColor redColor];
    //将按钮添加到自身
    [self addSubview:_myBtn];
  }
  return self;
}

@end

#import <UIKit/UIKit.h>

@interface MyViewController : UIViewController

@end

#import "MyViewController.h"
#import "MyView.h"

@interface MyViewController ()

@property (strong, nonatomic) MyView *myview;

@end

@implementation MyViewController

- (void)loadView
{
  MyView *myView = [[MyView alloc] initWithFrame: [[UIScreen mainScreen] bounds] ];
  self.view = myView;
  self.myview = myView;
  
  //在controller中设置按钮的目标-动作，其中目标是self，也就是控制器自身，动作是用目标提供的BtnClick:方法，
  [self.myview.myBtn addTarget:self
             action:@selector(BtnClick:)
        forControlEvents:UIControlEventTouchUpInside];
}

//MyView中的按钮的事件
- (void)BtnClick:(UIButton *)btn
{
  NSLog(@"Method in controller.");
  NSLog(@"Button clicked.");
}

 #import "AppDelegate.h"
#import "MyViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  
  self.window = [ [UIWindow alloc] initWithFrame: [[UIScreen mainScreen] bounds ] ];
  
  MyViewController *myVC = [[MyViewController alloc] init];
  self.window.rootViewController = myVC;
  
  self.window.backgroundColor = [UIColor whiteColor];
  [self.window makeKeyAndVisible];
          
  return YES;
}

#import <UIKit/UIKit.h>

//自定义的按钮协议，该协议实现了<NSObject>协议，协议的名称自定，不过不要和Apple的协议重名
@protocol myBtnDelegate <NSObject>

//协议中的方法，遵循该协议的类提供其具体的实现，协议有@optional和@required两个修饰符，默认情况下是@required
- (void) BtnClick:(UIButton *)btn;

@end

//MyView的接口
@interface MyView : UIView

//声明一个属性，这个属性用于指定谁来成为本类的代理，由于不能确定什么类型的对象会成为本类的代理，因此声明为id类型
@property (weak, nonatomic) id<myBtnDelegate> delegate;

@end

#import "MyView.h"

@interface MyView ()
//声明在.m中的按钮对外部不可见
@property (strong, nonatomic) UIButton *myBtn;

@end

@implementation MyView
//初始化
- (id)initWithFrame:(CGRect)frame
{
  self = [super initWithFrame:frame];
  if (self)
  {
    _myBtn = [[UIButton alloc] initWithFrame:CGRectMake(140, 100, 100, 50)];
    _myBtn.backgroundColor = [UIColor redColor];
    //为按钮设置目标-动作，其中目标是self即包含该按钮的view自身，动作是有目标（view）提供的myBtnClick：方法
    [_myBtn addTarget:self
          action:@selector(myBtnClick:) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:_myBtn];
  }
  
  return self;
}
//view中按钮的事件
- (void)myBtnClick:(UIButton *)btn
{
  NSLog(@"Method in view");
  //在回调代理方法时，首先判断自身的代理是否实现了代理方法，否则会导致崩溃
  //如果自身代理实现了代理方法，在该方法中回调代理实现的具体的代理方法
  if ( [self.delegate respondsToSelector:@selector(BtnClick:)] )
  {
    [self.delegate BtnClick: btn];
  }
  else
  {
    NSLog(@"BtnClick: haven't found in delegate.");
  }
  
}

@end

#import "MyViewController.h"
#import "MyView.h"
//声明该controller遵循 <myBtnDelegate>协议，因此需要实现协议中的方法
@interface MyViewController () <myBtnDelegate>
@end

@implementation MyViewController

- (void)loadView
{  //创建MyView类型的myView
  MyView *myView = [[MyView alloc] initWithFrame: [[UIScreen mainScreen] bounds] ];
  //将myView的代理设置为self，即当前controller自身
  myView.delegate = self;
  //将controller的view指向myView
  self.view = myView;
}

//该方法是代理中的方法，在controller中决定点击myBtn按钮后具体要做的事情，但controller并不能直接获取到myBtn
- (void)BtnClick:(UIButton *)btn
{
  NSLog(@"Method in controller.");
  NSLog(@"Button clicked.");
}