用 get 同步/异步 方式获取网络数据并输出

//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:10];
    //发送请求
    NSData* data=[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    //处理数据
    NSDictionary* dic=[NSJSONSerialization JSONObjectWithData:data options:0 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:10];
    //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:0 error:nil];
            //NSLog(@"%@",dic);
            NSDictionary* dicsk=dic[@"result"];
            NSDictionary* temp=dicsk[@"today"];
            NSLog(@"城市==%@",temp[@"city"]);
        }
        if (connectionError) {
            NSLog(@"Error");
        }
    }];