第八讲：ObjC 协议 Delegate 代理设计模式

转：http://tigercat1977.blog.163.com/blog/static/2141561122012111295321374/

第八讲：Obj-C 协议 Delegate 代理设计模式 

      代理设计模式 也叫做 委托设计模式
主要内容
      协议的具体用法
      如何实现代理
      代理两端如何通讯

案例 : 通过狗每隔一秒向主人叫一次                 类似C语言中的回调函数

  

通过狗每隔一秒向主人叫一次  

//  Dog.h
#import <Foundation/Foundation.h>
@protocol DogBark; // 这里声明后边的 DogBark 协议
// @protocol 表示协议前向声明
// @class Dog;  也可以，把后面的 DogBark 协议放到前边，声明 Dog
// @class 表示前向声明一个类
@interface Dog : NSObject
{
    int _ID;
    NSTimer *timer;  // 定时器
    int barkCount; // 叫的次数
    id <DogBark> delegate; //ownner 存狗的主人
}
@property int ID;
@property (assign) id <DogBark> delegate;

@end

// 定义一个人和狗通讯的方式 protocol
@protocol DogBark <NSObject>

- (void) bark:(Dog *)thisDog count:(int)count;

@end 

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

@implementation Dog
@synthesize ID = _ID;
@synthesize delegate;
- (id) init
{
    self = [super init];
    if (self)
    {
        timer = [NSTimer scheduledTimerWithTimeInterval:1.0f 
                                                 target:self
                                               selector:@selector(updateTimer:)
                                               userInfo:nil
                                                repeats:YES];
        // 创建一个定时器 每隔 1.0s 就调用 ［self updateTimer:nil］;
    }
    return self;
}

- (void) updateTimer:(id)arg
{
    barkCount++;
    NSLog(@"dog bark %d", barkCount);
    // 通知狗的主人  就是 delegate
    [delegate bark:self count:barkCount];
    // 调用 delegate 主人里面的 bark:count: 方法
    // 向主人回报
}
@end 

//  Person.h
#import <Foundation/Foundation.h>
#import "Dog.h"

@interface Person : NSObject <DogBark>
{
    Dog *_dog;
}
@property (retain) Dog *dog;
@end 

//  Person.m
#import "Person.h"
@implementation Person
@synthesize dog = _dog;

- (void) setDog:(Dog *)dog
{
    if (_dog != dog) {
        [_dog release];
        _dog = [dog retain];
        // 通知 _dog 的主人是 self
        [_dog setDelegate:self];
    }
}
- (Dog *) dog
{
    return _dog;
}
- (void) bark:(Dog *)thisDog count:(int)count
{
    // 当狗叫的时候来调用 xiaoLi 人的这个方法
    NSLog(@"Person this dog %d bark %d", [thisDog ID], count);
}
- (void) dealloc
{
    self.dog = nil;
    [super dealloc];
}
@end 

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

int main (int argc, const char * argv[])
{
    @autoreleasepool
    {
        NSLog(@"Hello, World!");
        Person *xiaoLi = [[Person alloc] init];
        Dog *dog = [[Dog alloc] init];
        [dog setID:10];
        
        [xiaoLi setDog:dog];
        [dog release];
        
        while (1)
        {
            [[NSRunLoop currentRunLoop] run];
        }
        
        [xiaoLi release];     
    }
    return 0;
}
/* 输出结果
 2012-12-17 21:45:18.909  Hello, World!
 2012-12-17 21:45:19.913  dog bark 1
 2012-12-17 21:45:19.914  Person this dog 10 bark 1
 2012-12-17 21:45:20.920  dog bark 2
 2012-12-17 21:45:20.923  Person this dog 10 bark 2
 2012-12-17 21:45:21.912  dog bark 3
 2012-12-17 21:45:21.913  Person this dog 10 bark 3
 2012-12-17 21:45:22.912  dog bark 4
 2012-12-17 21:45:22.913  Person this dog 10 bark 4
 2012-12-17 21:45:23.913  dog bark 5
 2012-12-17 21:45:23.914  Person this dog 10 bark 5
 2012-12-17 21:45:24.913  dog bark 6
 2012-12-17 21:45:24.914  Person this dog 10 bark 6
 2012-12-17 21:45:25.913  dog bark 7
 2012-12-17 21:45:25.914  Person this dog 10 bark 7
 ...........................................
 .......................
 ...............
*/

（本讲整理完）