原創帖子，轉載請註明出處：http://blog.csdn.net/sbvfhp/article/details/48112333

需求：有三個併發的通訊執行緒，三個通訊都結束後，進行一個回撥攔截（當然這個也可以用AFN提供的方法實現，這裡只是研究自己的一種實現）

-(void)viewDidLoad
{
    NSString *url1 = @"http://api.oupag.com/dev/api/shenzhentong.php?cardno=29444xxxx";
    
    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
    manager.operationQueue.maxConcurrentOperationCount = 3;

    [manager GET:url1 parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject){
        
        [self requestSuccessLast:responseObject];
        
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        [self requestFailLast:error];
    }];
    
    [manager GET:url1 parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject){
        [self requestSuccessLast:responseObject];
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        [self requestFailLast:error];
    }];
    
    [manager GET:url1 parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject){
        [self requestSuccessLast:responseObject];
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        [self requestFailLast:error];
    }];
}

-(void)requestSuccessLast:(id)response{
    _count++;
    
    if (_count==3) {
        NSLog(@"-------------以成功結束了-------------");
    }else{
        NSLog(@"第---%d-----次成功",_count);
    }
}

-(void)requestFailLast:(id)response{
    _count++;
    
    if (_count==3) {
        NSLog(@"-------------以失敗線束了-------------");
    }else{
        NSLog(@"第---%d-----次失敗",_count);
    }
}