How to post string data to API - ios

Question

I wanted to post a string data to API, I try to send it to server by using the below code. I've check api there by using the postman, it did not pass in the string data into the server. I do not know what is the problem and need help on this.
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:reqURLStr]];
[request setHTTPMethod:#"POST"];
**//Pass The String to server**
NSString *userUpdate =[NSString stringWithFormat:#"service_type=%#&ParcelSize=%#&ReceiverName=%#&MobileNumber=%#&Email=%#&DropOffHub=%#&PickupHub=%#" ,serviceType,pSize,rName,rMobile,rEmail,dropHubID,pickHubID];
NSData *data1 = [userUpdate dataUsingEncoding:NSUTF8StringEncoding];
[request setHTTPBody:data1];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];
[request setValue:[data makeRestAPICall:reqURLStr] forHTTPHeaderField:#"Authorization"];
NSError *err;
NSURLResponse *response;
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err];
NSString *resSrt = [[NSString alloc]initWithData:responseData encoding:NSASCIIStringEncoding];
NSLog(#"got response==%#", resSrt);
if(resSrt)
{
NSLog(#"got response");
}
else
{
NSLog(#"fail to connect");
}
return resSrt;

Answer 1

Simple answer
-(void)postJsonDataToServer{
NSDictionary *parameters = #{
#"service_type": serviceType,
#"ParcelSize": pSize,
#"ReceiverName": rName,
#"MobileNumber": rMobile,
#"Email" : rEmail,
#"DropOffHub" : dropHubID,
#"PickupHub" : pickHubID
};
NSData *data = [NSJSONSerialization dataWithJSONObject:parameters options:0 error:nil];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:#"http:/api/order/add"]];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json;charset=UTF-8" forHTTPHeaderField:#"content-type"];
NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
NSURLSessionUploadTask *dataTask = [session uploadTaskWithRequest: request
fromData:data completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(data != nil)
{
NSError *parseError = nil;
//If the response is in dictionary format
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
//OR
//If the response is in array format
NSArray *res = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
NSLog(#"The res is - %#",res);
}
else
NSLog(#"Data returned the parameter is nil here");
}];
[dataTask resume];
}