rails：上传图片时ios中的服务器内部错误(rails: server internal error in ios while uploading image)

 当我将图像文件上传到rails webrick服务器时，会提示内部错误“找不到临时目录”，并且没有接收请求。 
 
boundary = @"---------------------------14737809831466499882746641449";

NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"nickname\"\r\n\r\n%@\r\n", nickname] dataUsingEncoding:NSUTF8StringEncoding]];
dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: attachment; name=\"profile_image\"; filename=\"%@\"\r\n", @"19"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:UIImageJPEGRepresentation(profileImage, 1.0f)];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];


NSString *requestURL = @"http://0.0.0.0:3000/index";

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
NSString *contentLength = [NSString stringWithFormat:@"%lu", (unsigned long)[body length]];
[request setURL:[NSURL URLWithString:requestURL]];
[request setValue:contentType forHTTPHeaderField:@"Content-Type"];
[request setValue:contentLength forHTTPHeaderField:@"Content-Length"];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:body];

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

[connection start];

When I upload image file to rails webrick server, an internal error "Could not find a temporary directory" is prompted, and there is no receive request.
 
boundary = @"---------------------------14737809831466499882746641449";

NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"nickname\"\r\n\r\n%@\r\n", nickname] dataUsingEncoding:NSUTF8StringEncoding]];
dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:@"Content-Disposition: attachment; name=\"profile_image\"; filename=\"%@\"\r\n", @"19"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:UIImageJPEGRepresentation(profileImage, 1.0f)];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];


NSString *requestURL = @"http://0.0.0.0:3000/index";

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
NSString *contentLength = [NSString stringWithFormat:@"%lu", (unsigned long)[body length]];
[request setURL:[NSURL URLWithString:requestURL]];
[request setValue:contentType forHTTPHeaderField:@"Content-Type"];
[request setValue:contentLength forHTTPHeaderField:@"Content-Length"];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:body];

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

[connection start];

原文：https://stackoverflow.com/questions/31851837