You can try appending the variable's values to the posted data in the following manner :
// text parameter
[postbody appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"applicationId\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
NSString *parameterValue1=[dict objectForKey:@"applicationId"];
[postbody appendData:[parameterValue1 dataUsingEncoding:NSUTF8StringEncoding]];
[postbody appendData:[@"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
Hope that works for you. Above code is just an example of the parameter sent with the file upload.