使用NSMutableURLRequest和NSURLConnection 以Post方式上传照片

接下来我想用系统的NSURLConnection来实现这个功能：
首先我们要定义一个全局变量:
/**
 * 
请求返回数据
 */
@property (nonatomic, strong) NSMutableData *mResponseData;
实现代码：
//字典里面装的是你要上传的内容
NSDictionary *parameters = @{@"content": @"这是刚刚在线的官方网站www.baidu.com"};

//上传的接口
NSString* urlstring = @"http://superqq.com/";
//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:urlstring]
                                                        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(self.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= [parameters 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",[parameters 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", (int)[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response的data
if (conn) {
    _mResponseData = [[NSMutableData alloc] init];
}
NSURLConnectionDelegate的代理方法：
#pragma mark - NSURLConnectionDelegate

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
   [_mResponseData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
   [_mResponseData appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{

   NSDictionary *dic =  [NSJSONSerialization JSONObjectWithData:_mResponseData options:kNilOptions error:nil];
   NSLog(@"%@", dic);

}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
   NSLog(@"Error: %@", error);
}