ios有几种请求比如最常用的post，get等。get的参数会在URL地址里看到，假如存在用户名和密码会被大家看到这就非常不安全。这是可以选择post的方式。虽然他们都可以放一些请求参数。请求可能要设置一些参数什么的，以下举个例子是发送图片的。其他一些delete，put请求都是类似的。网上也有一些开源的类库是封装了一些网络请求的。比如asihttp这个类库封装的一些和网络交互的方便的请求。缺点是用别人的类库一旦别人升级改动你也得自己跟着改。

 

//分界线的标识符

        NSString *TWITTERFON_FORM_BOUNDARY = @"AaB03x";

        //根据url初始化request

        NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]

                                                               cachePolicy:NSURLRequestReloadIgnoringLocalCacheData

                                                           timeoutInterval:10];

        //分界线 --AaB03x

        NSString *MPboundary=[[NSString alloc]initWithFormat:@"--%@",TWITTERFON_FORM_BOUNDARY];

        //结束符 AaB03x--

        NSString *endMPboundary=[[NSString alloc]initWithFormat:@"%@--",MPboundary];

        //要上传的图片

        UIImage *image=[params objectForKey:@"pic"];

        //得到图片的data

        NSData* data = UIImagePNGRepresentation(image);

        //http body的字符串

        NSMutableString *body=[[NSMutableString alloc]init];

        //参数的集合的所有key的集合

        NSArray *keys= [params allKeys];

        

        //遍历keys

        for(int i=0;i<[keys count];i++)

        {

            //得到当前key

            NSString *key=[keys objectAtIndex:i];

            //如果key不是pic，说明value是字符类型，比如name：Boris

            if(![key isEqualToString:@"pic"])

            {

                //添加分界线，换行

                [body appendFormat:@"%@\r\n",MPboundary];

                //添加字段名称，换2行

                [body appendFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n",key];

                //添加字段的值

                [body appendFormat:@"%@\r\n",[params objectForKey:key]];           

            }

        }

        

        添加分界线，换行

        [body appendFormat:@"%@\r\n",MPboundary];

        //声明pic字段，文件名为boris.png

        [body appendFormat:@"Content-Disposition: form-data; name=\"pic\"; filename=\"boris.png\"\r\n"];

        //声明上传文件的格式

        [body appendFormat:@"Content-Type: image/png\r\n\r\n"];

        

        //声明结束符：--AaB03x--

        NSString *end=[[NSString alloc]initWithFormat:@"\r\n%@",endMPboundary];

        //声明myRequestData，用来放入http body

        NSMutableData *myRequestData=[NSMutableData data];

        //将body字符串转化为UTF8格式的二进制

        [myRequestData appendData:[body dataUsingEncoding:NSUTF8StringEncoding]];

        //将image的data加入

        [myRequestData appendData:data];

        //加入结束符--AaB03x--

        [myRequestData appendData:[end dataUsingEncoding:NSUTF8StringEncoding]];

        

        //设置HTTPHeader中Content-Type的值

        NSString *content=[[NSString alloc]initWithFormat:@"multipart/form-data; boundary=%@",TWITTERFON_FORM_BOUNDARY];

        //设置HTTPHeader

        [request setValue:content forHTTPHeaderField:@"Content-Type"];

        //设置Content-Length

        [request setValue:[NSString stringWithFormat:@"%d", [myRequestData length]] forHTTPHeaderField:@"Content-Length"];

        //设置http body

        [request setHTTPBody:myRequestData];

        //http method

        [request setHTTPMethod:@"POST"]; 

        

        //建立连接，设置代理

        NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];

        

        //设置接受resp*****e的data

        if (conn) {

            mResp*****eData = [[NSMutableData data] retain];

        }