//1.NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];request.HTTPMethod=@"POST";request.HTTPBody = [@"" dataUsingEncoding:NSUTF8StringEncoding];//2.NSURLSession *session=[NSURLSession sharedSession];NSURLSessionDataTask *dataTask=  [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {NSLog(@"NSURLSession加载数据。。。。post。。。。。%@",data);}];//3.[dataTask resume];

    //1.确定请求路径NSURL *url = [NSURL URLWithString:@"http://www.baidu.com"];//2.创建请求对象//请求对象内部默认已经包含了请求头和请求方法（GET）NSURLRequest *request = [NSURLRequest requestWithURL:url];//3.获得会话对象,并设置代理/*第一个参数：会话对象的配置信息defaultSessionConfiguration 表示默认配置第二个参数：谁成为代理，此处为控制器本身即self第三个参数：队列，该队列决定代理方法在哪个线程中调用，可以传主队列|非主队列[NSOperationQueue mainQueue]   主队列：   代理方法在主线程中调用[[NSOperationQueue alloc]init] 非主队列： 代理方法在子线程中调用           */NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];//4.根据会话对象创建一个Task(发送请求）NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request];//5.执行任务[dataTask resume];

 //1.接收到服务器响应的时候调用该方法
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler{//在该方法中可以得到响应头信息，即responseNSLog(@"didReceiveResponse--%@",[NSThread currentThread]);completionHandler(NSURLSessionResponseAllow);//注意：需要使用completionHandler回调告诉系统应该如何处理服务器返回的数据//默认是取消的/*NSURLSessionResponseCancel = 0,        默认的处理方式，取消NSURLSessionResponseAllow = 1,         接收服务器返回的数据NSURLSessionResponseBecomeDownload = 2,变成一个下载请求NSURLSessionResponseBecomeStream        变成一个流*/
}//2.接收到服务器返回数据的时候会调用该方法，如果数据较大那么该方法可能会调用多次
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data{NSLog(@"didReceiveData--%@",[NSThread currentThread]);//拼接服务器返回的数据

}
//3.当请求完成(成功|失败)的时候会调用该方法，如果请求失败，则error有值-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {NSLog(@"didCompleteWithError--%@",[NSThread currentThread]);if(error == nil){//解析数据,JSON解析请参考
                 }}

 /*    //1.网址NSURL *url=[NSURL URLWithString:@"http://www.baidu.com"];//2.请求NSURLRequest *request=[NSURLRequest requestWithURL:url];//3.队列NSOperationQueue *queue=[[NSOperationQueue alloc]init];//4.发送异步请求[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse * response, NSData *  data, NSError *  connectionError) {NSString *content=[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];NSLog(@"加载成功：%@",content);}];*///同步发送，要放到另一个线程里，防止阻塞；dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];NSURLResponse *response;NSData *data=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];//&指的是指针；NSString *content=[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];NSLog(@"NSURLConnection加载数据。。。。。。。：%@",content);});

 NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];// NSURLResponse *response;
   [NSURLConnection connectionWithRequest:request delegate:self];

//
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{NSLog(@"接到response");
}//
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{NSLog(@"接收数据");}//
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{NSLog(@"接收数据完成");}