//同步请求

    //创建NSString用来存储请求的网址

    NSString* str=@"http://v.juhe.cn/weather/index?format=2&cityname=沈阳&key=41cf6f9685a8776dc8384806c262ca0e";

    //用UTF8String格式转换成NSURL

    NSURL* url=[NSURL URLWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    //创建请求

    NSURLRequest* request=[[NSURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:];

    //发送请求

    NSData* data=[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

    //处理数据

    NSDictionary* dic=[NSJSONSerialization JSONObjectWithData:data options: error:nil];

    NSDictionary* dicsk=dic[@"result"];

    NSDictionary* temp=dicsk[@"today"];

    NSLog(@"城市:%@",temp[@"city"]);

    NSLog(@"%@",dicsk);

//异步请求

    //创建NSString用来存储请求的网址

    NSString* str=@"http://v.juhe.cn/weather/index?format=2&cityname=沈阳&key=41cf6f9685a8776dc8384806c262ca0e";

    //用UTF8String格式转换成NSURL

    NSURL* url=[NSURL URLWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    //创建请求

    NSURLRequest* request=[[NSURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:];

    //发送请求

    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        if (data) {

            //处理数据

            NSDictionary* dic=[NSJSONSerialization JSONObjectWithData:data options: error:nil];

            //NSLog(@"%@",dic);

            NSDictionary* dicsk=dic[@"result"];

            NSDictionary* temp=dicsk[@"today"];

            NSLog(@"城市==%@",temp[@"city"]);

        }

        if (connectionError) {

            NSLog(@"Error");

        }

    }];