设计模式：代理

1.通过中介公司找房子 

//1:协议声明:
#import <Foundation/Foundation.h>  
@protocol FindApartment <NSObject> 
　　-(void)findApartment;
@end

//2:代理角色声明(Agent.h)头文件声明
#import <Foundation/Foundation.h> 
#import "FindApartment.h" 
    @interface Agent : NSObject <FindApartment> 
@end

//3:代理角色实现（Agent.m）实现文件
#import "Agent.h" 
@implementation Agent 
-(void)findApartment{     
    NSLog(@"findApartment"); 
} 
@end

//4:真实角色声明（Person.h）头文件声明
#import <Foundation/Foundation.h>
#import "FindApartment.h" 
@interface Person : NSObject {   
  @private     NSString *_name;    
  id<FindApartment> _delegate; //委托人(具备中介找房子的协议) 
}
@property(nonatomic,copy) NSString *name;
@property(nonatomic,assign)id<FindApartment> delegate; 
-(id)initWithName:(NSString *)name withDelegate:(id<FindApartment>) delegate;
-(void)wantToFindApartment;
@end

//5:真实角色实现（Person.m）实现
#import "Person.h" 
//定义私有方法 
@interface Person()
 -(void)startFindApartment:(NSTimer *)timer; 
@end 
@implementation Person
 @synthesize name=_name; 
 @synthesize delegate=_delegate;
 -(id)initWithName:(NSString *)name withDelegate:(id<FindApartment>) delegate{     
    self=[super init];     
    if(self){         
        self.name=name;         
        self.delegate=delegate;     
    }    
    return self; 
 } 
 -(void)wantToFindApartment{     
    [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(startFindApartment:) userInfo:@"Hello" repeats:YES];     
 }  
 -(void)startFindApartment:(NSTimer *)timer{    
     //NSString *userInfo=[timer userInfo];     
    [self.delegate findApartment];
 }
@end

//6:测试代理main.m方法
#import <Foundation/Foundation.h> 
#import "Person.h" 
#import "Agent.h"
int main(int argc, const char * argv[]) {     
 @autoreleasepool {                  
    // insert code here...         
    NSLog(@"Hello, World!");         
    Agent *agent=[[Agent alloc]init];         
    Person *jack=[[Person alloc]initWithName:@"jack" withDelegate:agent];         
    [jack wantToFindApartment];         
    [[NSRunLoop currentRunLoop]run];         
    [jack autorelease];     
 }     
 return 0; 
}

2.代理设计模式的编码规范：

（1）一帮情况下，当协议属于谁，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那个类的类名开头，后面跟上protocol或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，一个类中的代理的名称叫做 delegate;

（6）当一个类要成为另外一个类的代理的时候，一般情况下：

         .h中用   @protocol 协议名称;   来告诉当前类，这是一个协议。

         .m中 用   #import 类名  来真正导入协议的声明

 例子：学生找房子

Student.h
#import <Foundation/Foundation.h>
@class Student;

//通过代理来找房子，所以首先定义一个协议
@protocol StudentProtocol <NSObject>

-(void)studentFindHourse:(Student *)student;

@end


@interface Student : NSObject

//代理
@property(nonatomic, strong) id<StudentProtocol> delegate;

//找房子
-(void)findHourse;

@end

----------------------------------------------------------------------------------------
Student.m
#import "Student.h"

@implementation Student

//学生通过代理找房子
-(void)findHourse{
    NSLog(@"学生想找房子");
    if ([self.delegate respondsToSelector:@selector(studentFindHourse:)]) {
        [self.delegate studentFindHourse:self];
    }
}

@end

----------------------------------------------------------------------------------------
LoveHome.h
#import <Foundation/Foundation.h>
@protocol StudentProtocol;//标明StudentProtocol是一个协议

//爱家，专做销售房子的代理
@interface LoveHome : NSObject<StudentProtocol>

@end

----------------------------------------------------------------------------------------
LoveHome.m
#import "LoveHome.h"
#import "Student.h"

@implementation LoveHome

-(void)studentFindHourse:(Student *)student{
    NSLog(@"%s 帮忙找房子",__func__);
}

@end

----------------------------------------------------------------------------------------
main.m
#import <Foundation/Foundation.h>
#import "Student.h"
#import "LoveHome.h"

int main(int argc, const char * argv[]) {

    Student *stu = [[Student alloc] init];
    LoveHome *lh = [[LoveHome alloc] init];
    stu.delegate = lh;
    [stu findHourse];

    return 0;
}

根据规范，重写1：

//Person.h
#import <Foundation/Foundation.h>
@class Person;

@protocol PersonProtocol <NSObject>

-(void)personWantToFindApartment:(Person *)person;

@end

//Person要找房子
@interface Person : NSObject

@property (nonatomic, assign) NSString *name;

//找房子的代理
@property (nonatomic, strong) id<PersonProtocol>delegate;

//构造方法
-(instancetype)initWithName:(NSString *)name withDelegate:(id<PersonProtocol>)delegate;

//找房子
-(void)wantToFindApartment;

@end



//Person.m
#import "Person.h"

//定义私有方法
@interface Person()

-(void)startFindApartment:(NSTimer *)timer;

@end

//实现Person
@implementation Person

-(instancetype) initWithName:(NSString *)name withDelegate:(id<PersonProtocol>)delegate{
    self = [super init];
    if (self) {
        self.name = name;
        self.delegate = delegate;
    }
    return self;
}

-(void) wantToFindApartment{
    [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(startFindApartment:) userInfo:@"代理找房子" repeats:YES];
}

//实现私有方法
-(void) startFindApartment:(NSTimer *)timer{
    NSString *info = [timer userInfo];
    NSLog(@"1");
    if ([self.delegate respondsToSelector:@selector(personWantToFindApartment:)]) {
        NSLog(@"%@",info);
        [self.delegate personWantToFindApartment:self];
    }
}

@end



//Agent.h
//代理
#import <Foundation/Foundation.h>
@protocol PersonProtocol;

@interface Agent : NSObject<PersonProtocol>

@end


//Agent.m
#import "Agent.h"
#import "Person.h"

@implementation Agent

-(void)personWantToFindApartment:(Person *)person{
    NSLog(@"%s 代理帮忙找房子",__func__);
}

@end



//main.m
#import <Foundation/Foundation.h>
#import "Person.h"
#import "Agent.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Agent *a = [[Agent alloc] init];
        Person *p = [[Person alloc] initWithName:@"keen" withDelegate:a];

        [p wantToFindApartment];

        [[NSRunLoop currentRunLoop] run];
    }


    return 0;
}