POST json string in NSURLSession - ios

Question

In my iOS app I am posting json string to server using NSURLConnection like this.
post_string = #"{"function":"getHuddleDetails", "parameters": {"user_id": "167","location_id": "71","huddle_id": "328","checkin_id": "1287"},"token":""}"
-(void)myServerRequests:(NSString *)post_string{
NSData *postData = [post_string dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength = [NSString stringWithFormat:#"%d", [postData length]];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:[NSURL URLWithString:#"http://www.myServerURl.com/jsonpost"]];
[request setTimeoutInterval:100];
[request setHTTPMethod:#"POST"];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/x-www-form-urlencoded;charset=UTF-8" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:postData];
conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
if (conn) {
webData = [[NSMutableData alloc]init];
}
}
And posting multipart/form-data (not JSON) using NSURLSession using below code
-(void)myFunction:(NSString *)user_name paswd:(NSString *)pass_word {
NSString *boundary = [self boundaryString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:#"http://www.myServerURl.com/formpost"]];
[request setHTTPMethod:#"POST"];
[request addValue:[NSString stringWithFormat:#"multipart/form-data; boundary=%#",boundary] forHTTPHeaderField:#"Content-Type"];
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration];
NSMutableData *postbody = [NSMutableData data];
[postbody appendData:[[NSString stringWithFormat:#"\r\n--%#\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"username\"\r\n\r\n%#", user_name] dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[[NSString stringWithFormat:#"\r\n--%#\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"password\"\r\n\r\n%#", pass_word] dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[[NSString stringWithFormat:#"\r\n--%#\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[[NSString stringWithFormat:#"\r\n--%#--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
NSURLSessionUploadTask *task = [session uploadTaskWithRequest:request fromData:postbody completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSAssert(!error, #"%s: uploadTaskWithRequest error: %#", __FUNCTION__, error);
NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] ;
}];
[task resume];
}
This works perfectly fine with NSURLSession, but when I tried to post json string (converted it to NSDATA and posted using NSURLSession), it is not working.
Why it happens ?
Thanks in advance

Answer 1

If you want to send JSON to a server you should set the content type accordingly to application/json and your content is actually just that: the JSON encoded preferably in UTF-8.
In your method myServerRequests: you set content type application/x-www-form-urlencoded - but you don't setup the corresponding content correctly. How to do this can be read here: URL-encoded form data. Additionally, specifying a charset parameter has no effect at all.
In case you want to send a string parameter for a application/x-www-form-urlencoded content type, you should also not use a lossy conversion. Instead use UTF-8. Note that NSStrings length returns the number of UTF-16 code points - which is not the same as the number of bytes of an UTF-8 encoded string.
Recap:
Don't use application/x-www-form-urlencoded content type. Instead:
Content-Type = application/json
Content-Length = <length in bytes of the UTF-8 encoded JSON>
When you fix these issues, the request should be OK.
When using a multipart/form-data request I strongly recommend to use a network library. Doing this by hand is too error prone and you would need to read at least 300 RFCs to know that you are doing it correctly ;)