iOS编程（4）上传文件和字符串_ios开发传输字符串-优快云博客

本文介绍了如何在iOS中同时使用POST方法上传图片和NSString。通过参考ios Upload Image and Text using HTTP POST，详细讲解了实现过程，并提供了UIImage到NSData的压缩函数代码，确保图片不超过指定大小。

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一、介绍

用POST上传NSString或者图片都比较简单，但是一起上传的时候就有点难度，这里说一下图片和字符串怎么一起POST

二、实现

参考ios Upload Image and Text using HTTP POST

附上代码&解释

//一共传递3个变量，其中nickname和sex是NSString的对象而photoFile是UIImage
//设置好url后初始化request，接下来需要做的有这几件事情：1.设置multipart&boundary，2.nickname、sex&photoFile加入到NSMutableData类型的body变量中，其中每个变量之间要设置分界线，3.将设置好的body作为request的HTTPbody，然后用NSURLSessionDataTask来发送即可
//注意：1、[body appendData:[[NSString stringWithFormat:@"--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];这里的--不能少，不然会失败
//2、\r\n用于换行
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request.HTTPMethod = @"POST";
NSString *boundary = @"----WebKitFormBoundary7MA4YWxkTrZu0gW";
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
[request addValue:contentType forHTTPHeaderField: @"Content-Type"];

NSMutableData *body = [NSMutableData data];
//nickname
[body appendData:[[NSString stringWithFormat:@"--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=%@\r\n\r\n",@"nickname"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[self.writeName.text stringByAppendingString:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
//sex
[body appendData:[[NSString stringWithFormat:@"--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n",@"sex"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"1\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
//photo file
[body appendData:[[NSString stringWithFormat:@"--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"headPhoto.jpg\"\r\n", @"photoFile"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[@"Content-Type: image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:imageData];
[body appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

//set http body
NSString *postLength = [NSString stringWithFormat:@"%lu", (unsigned long)[body length]];
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:body];

三、微小的工作

上传图片的时候应该保证图片不超过指定大小，这里在将UIImage转成NSData的时候，用到了UIImageJPEGRepresentation函数的压缩系数，用loop的方法保证NSData的大小，附上压缩函数代码

- (NSData *)compressImage:(UIImage *)image {
    CGFloat compression = 0.9f;
    CGFloat maxCompression = 0.1f;
    int maxFileSize = 2048000;

    NSData *imageData = UIImageJPEGRepresentation(self.chooseHeadPhoto.imageView.image, compression);

    while ([imageData length] > maxFileSize && compression > maxCompression)
    {
        compression -= 0.1;
        imageData = UIImageJPEGRepresentation(self.chooseHeadPhoto.imageView.image, compression);
    }
    return imageData;
}