NSString *urlString = @"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id=";
    NSLog(@"%@",urlString);

//    下载数据
//    通过地址生成NSURL对象
    NSError *error = nil;
    NSURL *url = [NSURL URLWithString:urlString];
    NSString *content = [[NSString alloc]initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
    if (error == nil) {
        NSLog(@"content = %@",content);
    }
    else{
        NSLog(@"下载失败");
    }
    
//    项目中怎么使用
//    1.同步形式下载，initWithContentsOfURL下载完了之后才会返回造成界面假死，不能使用
//    2.使用异步下载（NSURLConnection 异步下载）

 NSString *urlString = @"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id=";
    
//    发送同步URL请求
//    NSURLRequest URL请求
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSError *error = nil;
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&error];
    if (error == nil) {
        NSString *str = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"str = %@",str);
    }
    else{
        NSLog(@"下载失败");
    }

-(void)testtestNSURLConnectionAsyncDownloadData
{
    NSString *urlString = @"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id=";
    
//    初始化
    _data = [[NSMutableData alloc]init];
//    发起一个异步的URL连接请求
//    异步: 执行了方法之后开始下载，立即返回，下载过程在后台（多线程）执行
    _connection = [[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:urlString]] delegate:self startImmediately:YES];
    NSLog(@"initWithRequest执行完成");
    
}

//代理方法：接收到服务器的响应执行
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"接收到服务器的响应");
}

//代理方法：接收到数据的时候执行
//注意:但数据比较大的时候可能多次执行
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [_data appendData:data];
}

//代理方法：数据下载完成了
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *str= [[NSString alloc]initWithData:_data encoding:NSUTF8StringEncoding];
    NSLog(@"str = %@",str);
    
//    最简单的现实名字
//    解析JSON
//    作用：JSON数据转化为NSDictionary或NSArray
    NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:_data options:NSJSONReadingMutableContainers error:nil];
    NSArray *appList = dic[@"applications"];
    for (NSDictionary *appDic in appList) {
        NSLog(@"name = %@",appDic[@"name"]);
    }
}

//代理方法：数据下载失败
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"error = %@",error);
}

{
  "list" : [
    {
      "IsXuanZuo" : 0,
      "Name" : "汪峰2014“峰暴来临”超级巡回演唱会 重庆站",
      "PriceStr" : "180,280,380,480,680,980,1280",
      "ProjectID" : 66611,
      "ShowTime" : "2014.11.01",
      "SiteStatus" : 8,
      "Summary" : "【先付预告】2014年5月12日12:08开启先付！",
      "VenId" : 258,
      "VenName" : "重庆奥体中心",
      "cityname" : "重庆市",
      "priceName" : "180-1280元"
    },
    {
      "IsXuanZuo" : 0,
      "Name" : "莫文蔚20周年巡回演唱会 郑州站",
      "PriceStr" : "480,680,880,1280,1680,2014",
      "ProjectID" : 66313,
      "ShowTime" : "2014.07.26",
      "SiteStatus" : 8,
      "Summary" : "【客户端专享】480元少量稀缺票客户端独家售卖！",
      "VenId" : 942,
      "VenName" : "郑州国际会展中心",
      "cityname" : "郑州市",
      "priceName" : "480-2014元"
    },
    {
      "IsXuanZuo" : 0,
      "Name" : "王力宏2014MUSIC-MANII“火力全开”世界巡回演唱会—北京站",
      "PriceStr" : "280,380,480,580,880,1280,1680",
      "ProjectID" : 66052,
      "ShowTime" : "2014.06.14",
      "SiteStatus" : 8,
      "Summary" : "坦克上台火力十足，打造音乐战役！全新演绎经典作品，体验超凡音乐魅力！",
      "VenId" : 392,
      "VenName" : "国家体育场",
      "cityname" : "北京市",
      "priceName" : "280-1680元"
    }
  ]
}