iOS中delegate的使用

一、首先介绍Protocol

1、协议protocol说明

protocol：定义公用的一套接口，但不提供具体的实现方法。
协议约定可选择实现的方法和必须实现的方法。

@required：必须实现的方法
@optional：可选是否实现的方法

2、协议protocol的使用

//创建协议文件protocolDelegate

//1.new file -->Objective-C File-->选择Protocol，创建Protocol文件
//protocol文件只有.h文件，只声明方法。
#import <Foundation/Foundation.h>

@protocol protocolDelegate <NSObject>
@required
//必须实现的方法
- (void)eat;
- (void)drink;

// 可选实现的方法
@optional
- (void)readBook;
- (void)writeCode;
@end

//创建student类和programmer类具体实现对应方法

//2.创建student类
//Student.h
#import <Foundation/Foundation.h>
#import "protocolDelegate.h"

@interface Student : NSObject <protocolDelegate>

@end
//Student.m
#import "Student.h"

@implementation Student

- (void)eat {
    NSLog(@"%@",@"我是学生，我必须得吃饭，我吃米饭");
}

- (void)drink {
    NSLog(@"%@",@"我是学生，我必须得喝水，我喝饮料");
}

- (void)readBook {
    NSLog(@"%@",@"我是学生，我会读书");
}

@end

//3.创建Programma类
//Programma.h
#import <Foundation/Foundation.h>
#import "protocolDelegate.h"

@interface Programmer : NSObject <protocolDelegate>

@end
//Programma.m
#import "Programmer.h"

@implementation Programmer
- (void)eat {
    NSLog(@"%@",@"我是工程师，我必须得吃饭，我吃火锅");
}

- (void)drink {
    NSLog(@"%@",@"我是工程师，我必须得喝水，我喝啤酒");
}

- (void)writeCode {
    NSLog(@"%@",@"我是工程师，我会写代码");
}
@end

//调用方法

//在viewcontroller里调用
#import "ViewController.h"
#import "Student.h"
#import "Programmer.h"

@interface ViewController ()

@property (nonatomic, strong) Student       *student;
@property (nonatomic, strong) Programmer    *programmer;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self dinerTogether];
}

// 聚餐
- (void)dinerTogether {
    [self eatTogether];
    [self drinkTogether];
    [self doMySelf];
}
- (void)eatTogether {
    if ([self.student respondsToSelector:@selector(eat)]) {
        [self.student eat];
    }
    if ([self.programmer respondsToSelector:@selector(eat)]) {
        [self.programmer eat];
    }

}
- (void)drinkTogether {
    if ([self.student respondsToSelector:@selector(drink)]) {
        [self.student drink];
    }
    if ([self.programmer respondsToSelector:@selector(drink)]) {
        [self.programmer drink];
    }

}
- (void)doMySelf {
    if ([self.student respondsToSelector:@selector(readBook)]) {
        [self.student readBook];
    }
    if ([self.programmer respondsToSelector:@selector(writeCode)]) {
        [self.programmer writeCode];
    }

}

#pragma mark - getter and setter

- (Student *)student {
    if (!_student) {
        _student = [[Student alloc] init];
    }
    return _student;
}
- (Programmer *)programmer {
    if (!_programmer) {
        _programmer = [[Programmer alloc] init];
    }
    return _programmer;
}

@end

注：一般多个类要实现共同的方法，又各自有自己要实现的方法时，可使用Protocol

一、delegate简介

代理设计模式，是iOS中一种消息传递的方式，由代理对象、委托者、协议组成。

• 协议：用来指定代理可以做什么，必须做什么。

• 代理：根据指定协议，完成委托方需要实现的方法。
• 委托：根据指定协议，指定代理必须完成和可以完成方法。

二、delegate的使用

1、传值

//下一控制器传值给上一控制器
//下一控制器NextViewController文件

//NextViewController.h文件

#import <UIKit/UIKit.h>
@protocol NextViewControllerDelegate <NSObject>
- (void)sendValue:(NSString *)string;
@end

@interface NextViewController : UIViewController
@property (nonatomic, weak) id<NextViewControllerDelegate> delegate;
@end

//NextViewController.m文件
#import "NextViewController.h"

@interface NextViewController ()
//创建一个TextField输入要传端值
@property (nonatomic, strong) UITextField *tf_sendValue;
//创建返回上一控制器的按钮
@property (nonatomic, strong) UIButton *btn_backVc;
@end

@implementation NextViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    // 添加TextField
    UITextField *tf_sendValue = [[UITextField alloc]init];
    tf_sendValue.frame = CGRectMake(0, 100, self.view.frame.size.width, 30);
    tf_sendValue.textAlignment = 1;
    tf_sendValue.placeholder = @"请输入要传递的值";
    self.tf_sendValue = tf_sendValue;
    [self.view addSubview:tf_sendValue];
    
    // 添加返回上一控制器的按钮
    UIButton *btn_backVc = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 150, 35)];
    [btn_backVc setTitle:@"返回上一控制器" forState:UIControlStateNormal];
    [btn_backVc setBackgroundColor:[UIColor redColor]];
    btn_backVc.center = self.view.center;
    self.btn_backVc = btn_backVc;
    [self.view addSubview:btn_backVc];
    //添加点击事件
    [self.btn_backVc addTarget:self action:@selector(clickBackBtn) forControlEvents:UIControlEventTouchUpInside];
}
- (void)clickBackBtn{

    [self.navigationController popViewControllerAnimated:YES];
    NSString *str = self.tf_sendValue.text;
    if (str.length>0) {
        
        if ([self.delegate respondsToSelector:@selector(sendValue:)]) {
            [self.delegate sendValue:str];
        }
    }
}
@end

//上一控制器遵循协议，实现代理方法，获取传递的值

//ViewController.m文件
#import "ViewController.h"
#import "NextViewController.h"
@interface ViewController ()<NextViewControllerDelegate>
//创建一个Label显示下一界面传过来的值
@property (nonatomic, strong) UILabel *lb_showStr;
//创建push下一界面按钮
@property (nonatomic, strong) UIButton *btn_nextVc;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.title = @"第一个控制器";
    self.view.backgroundColor = [UIColor whiteColor];

    // 添加lb_showStr
    UILabel *lb_showStr = [[UILabel alloc]init];
    lb_showStr.frame = CGRectMake(0, 100, self.view.frame.size.width, 30);
    lb_showStr.textAlignment = NSTextAlignmentCenter;
    lb_showStr.text = @"显示下一界面的传值";
    self.lb_showStr = lb_showStr;
    [self.view addSubview:lb_showStr];
    // 添加push下一控制器按钮
    UIButton *btn_nextVc = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 150, 35)];
    [btn_nextVc setTitle:@"push下一界面" forState:UIControlStateNormal];
    [btn_nextVc setBackgroundColor:[UIColor redColor]];
    btn_nextVc.center = self.view.center;
    self.btn_nextVc = btn_nextVc;
    [self.view addSubview:btn_nextVc];
    //添加点击事件
    [self.btn_nextVc addTarget:self action:@selector(clickPushBtn) forControlEvents:UIControlEventTouchUpInside];
}
- (void)clickPushBtn{
    NextViewController *nextVc = [[NextViewController alloc]init];
    [self.navigationController pushViewController:nextVc animated:YES];
    nextVc.delegate = self;
}
- (void)sendValue:(NSString *)string{
    self.lb_showStr.text = string;
}
@end

2、传递事件

//点击自定义view，传递view点击事件

//1.MyView.h
#import <UIKit/UIKit.h>

@protocol MyViewDelegate <NSObject>
- (void)myViewDelegateFunc;

@end

@interface MyView : UIView

//声明代理属性
@property (nonatomic, weak) id<MyViewDelegate> myViewDelegate;

@end

//2.MyView.m
#import "MyView.h"

@implementation MyView

//点击view，响应代理方法
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

    if ([_myViewDelegate respondsToSelector:@selector(myViewDelegateFunc)]) {
        [_myViewDelegate myViewDelegateFunc];
    }
}
@end

//实现代理方法

#import "ViewController.h"
#import "MyView.h"

@interface ViewController ()<MyViewDelegate>
@property (nonatomic, strong) MyView *myView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    MyView *myView = [[MyView alloc]init];
    myView.myViewDelegate = self;
    self.myView = myView;
    myView.backgroundColor = [UIColor redColor];
    myView.frame = CGRectMake(100, 100, 100, 100);
    myView.center = self.view.center;
    myView.userInteractionEnabled = YES;
    
    [self.view addSubview:self.myView];
}
#pragma mark - myViewDelegate代理方法
- (void)myViewDelegateFunc{
    NSLog(@"myViewDelegate的代理 点击view");
}
@end

注：代理实现了不同视图之间的数据交互，只有某一事件触发才会被调用。在使用代理时，代理者要遵循代理，设置代理，实现代理方法。只有设置了代理，才能调用代理方法。