在网络编程中，如果需要上传图片，那么他的方法将会和普通的上传数据不同，下面将讲解如何上传图片。

环境信息：

Mac OS X 10.9.5

Xcode 5.1.1

IOS 7.1

正文：

- (NSURLRequest *)configPostImageURLWithMethod:(NSString *)method parameters:(NSDictionary *)parameters {
    
    NSString *TWITTERFON_FORM_BOUNDARY = @"AaB03x";
    //根据url初始化request
    NSMutableURLRequest* request = [NSMutableURLRequestrequestWithURL:[NSURLURLWithString:method]
                                                           cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                                       timeoutInterval:10];
    
    NSString *boundary = [NSStringstringWithFormat:@"--%@",TWITTERFON_FORM_BOUNDARY];
    
    NSString *endMPboundary = [NSStringstringWithFormat:@"%@--",boundary];
    //要上传的图片
    UIImage *image = [parameters objectForKey:@"pic"];
    //得到图片的data
    NSData* data = UIImagePNGRepresentation(image);
    //http body的字符串
    NSMutableString *body = [NSMutableStringstring];
    //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", boundary];
            //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", boundary];
    //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 = [NSStringstringWithFormat:@"\r\n%@",endMPboundary];
    //声明myRequestData，用来放入http body
    NSMutableData *myRequestData = [NSMutableDatadata];
    //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 = [NSStringstringWithFormat:@"multipart/form-data; boundary=%@",TWITTERFON_FORM_BOUNDARY];
    //设置HTTPHeader
    [request setValue:content forHTTPHeaderField:@"Content-Type"];
    //设置Content-Length
    [request setValue:[NSStringstringWithFormat:@"%d", [myRequestData length]] forHTTPHeaderField:@"Content-Length"];
    //设置http body
    [request setHTTPBody:myRequestData];
    //http method
    [request setHTTPMethod:@"POST"];
    
    return request;
}

注：在使用这个方法的时候，图片的key必须是pic。