head first 读书笔记：观察者模式（openfire 消息通知 demo）

场景：我们要从openfire服务器获取消息，然后同步更新到最近联系人界面和正在聊天的界面。此系统必须可扩展（公布一组API,让其他开发人员也可以写出自己的即时通讯），也就是用户可以自己增加或者删除接收消息的界面。

直接上代码：

父类

@interface Subject : NSObject

//注册监听者

- (void)registObserver:(Observer *)o;

//移除监听者

- (void)removeObserver:(Observer *)o;

//通知监听者

- (void)notifyObserver;

@end

@interface Observer : NSObject

//更新

- (void)updateDispayWithContent:(NSString *)content fromPeople:(NSString *)from toPeople:(NSString *)to;

@end

子类：

@interface Openfire : Subject

//发送消息

- (void) sendMessage:(NSString *)content fromPoeple:(NSString *)from toPeople:(NSString *)to;

@end

@interface Openfire()

@property (retain, nonatomic) NSMutableArray *observers;

@property (retain, nonatomic) NSString *fromPeople;

@property (retain, nonatomic) NSString *toPeople;

@property (retain, nonatomic) NSString *messageContent;

@end

@implementation Openfire

- (void)dealloc{

    

    [self.observers release];

    self.observers = nil;

    

    [super dealloc];

}

- (id)init{

    

    self = [super init];

    

    if (self) {

        

        self.observers = [[NSMutableArray alloc] init];

        

    }

    return self;

}

//创建数据库单例模式

+ (id)shareOpenfire{

    

    static dispatch_once_t openfireToken;

    static id shareOpenfire = nil;

    

    dispatch_once(&openfireToken, ^{

        shareOpenfire = [[[self class] alloc] init];

    });

    return shareOpenfire;

}

//注册监听者

- (void)registObserver:(Observer *)o{

    

    [self.observers addObject:o];

}

//移除监听者

- (void)removeObserver:(Observer *)o{

    

    NSInteger i = [self.observers indexOfObject:o];

    

    if (i>=0 && i<[self.observers count]) {

        

        [self.observers removeObjectAtIndex:i];

    }

}

//通知监听者

- (void)notifyObserver{

   

    for (int i=0; i<[self.observers count]; i++) {

        

        Observer *o = [self.observers objectAtIndex:i];

        

        [o updateDispayWithContent:self.messageContent fromPeople:self.fromPeople toPeople:self.toPeople];

    }

}

//收到消息

- (void)receiveMessage{

    [self notifyObserver];

}

//发送消息

- (void) sendMessage:(NSString *)content fromPoeple:(NSString *)from toPeople:(NSString *)to{

    self.messageContent = content;

    self.fromPeople = from;

    self.toPeople = to;

    

    [self receiveMessage];

}

@end

@interface Chat : Observer

//初始化

- (id)initWithSubject:(Subject *)obj;

@end

@interface Chat()

@property (retain, nonatomic) Subject *openfire;

@end

@implementation Chat

- (void)dealloc{

    

    if (self.openfire) {

        

        [self.openfire removeObserver:self];

        

        [self.openfire release];

        self.openfire = nil;

    }

    

    [super dealloc];

}

//初始化

- (id)initWithSubject:(Subject *)obj{

    self = [super init];

    

    if (self) {

        

        if (obj) {

            self.openfire = obj;

            

            [self.openfire registObserver:self];

        }

    }

    

    return self;

}

//更新

- (void)updateDispayWithContent:(NSString *)content fromPeople:(NSString *)from toPeople:(NSString *)to{

    [self displayMessage:content fromPeople:from toPeople:to];

}

//显示

- (void)displayMessage:(NSString *)content fromPeople:(NSString *)from toPeople:(NSString *)to{

    

    

    NSLog(@"chat收到消息：%@ ， from：%@ ， to：%@", content, from, to);

    

}

@end

测试代码；

    Openfire *o = [[Openfire alloc] init];

    Chat *c = [[Chat alloc]initWithSubject:o];

    Recent *r = [[Recent alloc]initWithSubject:o];

    

    [o sendMessage:@"测试。。。" fromPoeple:@"lichenglong" toPeople:@"ping"];

    [o sendMessage:@"test。。。" fromPoeple:@"lichenglong" toPeople:@"li"];

    [o sendMessage:@"hello。。。" fromPoeple:@"lichenglong" toPeople:@"lee"];

    [o sendMessage:@"你好。。。" fromPoeple:@"lichenglong" toPeople:@"chen"];

    [o release];

    [c release];

    [r release];