Objective-C之代理设计模式小实例

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代理设计模式小实例

协议的应用场景之一：代理模式

需求：

用代理实现学生找房子, 不具备找房子的能力
所以学生可以找另一个对象来帮它找房子, 那么另一个对象就是学生的代理

UML类图：

类图关系分析：

+ 两个对象：Student(学生用户)，LinkHouse(代理者)
+ LinkHouse是属于Student的代理，所以这里是(has a)拥有的组合关系
    + 所以：LinkHouse对象可以作为Student类里的一个对象数据类型的属性
    + 另外：因为不确定代理的具体类型，用id万能数据类型作为属性的声明类型
    + 在这里id数据类型后面需要<代理的名称>，例：id \<LinkHouse\>。
        - 协议写在数据类型的右边, 明确的标注如果想给该变量赋值, 那么该对象必须遵守某个协议

代码使用代理需要注意的地方

• Student的需求方法中(这里是findHouse找房子的行为)调用代理者(LinkHouse)的所能提供的方法(比如findHouse，要是这个代理不能满足需求用户的需求，那留他有啥用)

• 协议一般都是需求用户提出来的协议，比如我去相亲，对对方我心里肯定或多或少对对方有一些基本要求(比如会洗衣服做饭什么的)，这些就是我提出来的协议。所以要遵循协议的编写规范(比如：一般情况下, 当前协议属于谁, 我们就将协议定义到谁的头文件中)

• 协议的编写规范:

  • 1.一般情况下, 当前协议属于谁, 我们就将协议定义到谁的头文件中
  • 2.协议的名称一般以它属于的那个类的类名开头, 后面跟上protocol或者delegate
  • 3.协议中的方法名称一般以协议的名称protocol之前的作为开头
  • 4.一般情况下协议中的方法会将触发该协议的对象传递出去
  • 5.一般情况下一个类中的代理属于的名称叫做 delegate
  • 6.当某一个类要成为另外一个类的代理的时候, 一般情况下在.h中用@protocol 协议名称;告诉当前类 这是一个协议.在.m中用#import真正的导入一个协议的声明

接下来进入实例代码阶段：

Student.h代码：

 #import <Foundation/Foundation.h>
 #import "StudentFindHouse.h"
 @class LinkHouse;

 @interface Student : NSObject

 @property (nonatomic,strong)id<StudentFindHouse> delegate;

 -(void)findHouse;

 @end

Student.m代码：

 #import "Student.h"
 #import "LinkHouse.h"

 @implementation Student

 -(void)findHouse{
     if ([self.delegate respondsToSelector:@selector(findHouse)]) {
         [self.delegate findHouse];
     }
 }

 @end

---

然后写出Student的类的协议，StudentFindHouse.h：

 #import <Foundation/Foundation.h>

 @protocol StudentFindHouse <NSObject>

 -(void)findHouse;

 @end

---

LinkHouse.h代码：

 #import <Foundation/Foundation.h>

 #import "StudentFindHouse.h"

 @interface LinkHouse : NSObject <StudentFindHouse>

 -(void)findHouse;

 @end

LinkHouse.m代码：

 #import "LinkHouse.h"

 @implementation LinkHouse 

 -(void)findHouse{
     NSLog(@"%s 帮student找房子。",__FUNCTION__);
 }

 @end

---

main.m代码以及然后运行的结果：