iOS NSMutableURLRequest 上传图片

- (void)postImage:(UIImage *)_image
{
    //分界线的标识符
    NSString *TWITTERFON_FORM_BOUNDARY = @"AaB03x";
    //根据url初始化request
    NSInteger schoolID = [[BaseUser shareInstance].userIdentity.school_id integerValue];
    NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"url"]
                                                           cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                                       timeoutInterval:];
    //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= _image;
    //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
    NSDictionary *param = @{};
    NSArray *keys = [[param keyValues] allKeys];

    //遍历keys
    for(int i=;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",[[param keyValues] 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 sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        if (connectionError) {

        }else{
             NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
            NSLog(@"上传成功");
        }
    }];

}