NSInvalidArgumentException in sending POST request to HTTP - ios

Question

I'm writing simple code which is sending me response from http server after sending a POST request to it but if I try moving everything to another file XCode shows me this error:
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'data parameter is nil'
Here are the two files I'm using to make this work:
#import "HTTPRequestHandler.h"
#interface HTTPRequestHandler ()
#property (strong, nonatomic) NSURL *requestURL;
#property (strong, nonatomic) NSData *httpBody;
#property (strong, nonatomic) NSMutableData *responseData;
#end
#implementation HTTPRequestHandler
- (id)initWithURL:(NSString *)url body:(NSString *)body
{
if (self = [super init]) {
self.requestURL = [[NSURL alloc] initWithString:url];
self.httpBody = [body dataUsingEncoding:NSUTF8StringEncoding];
}
return self;
}
- (void)makeConnectionWithRequest
{
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:self.requestURL];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:self.httpBody];
[NSURLConnection connectionWithRequest:request delegate:self];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSLog(#"Dane doszły 1");
[self.responseData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSLog(#"Dane doszły 2");
[self.responseData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(#"Dane doszły 3");
NSDictionary *recievedData = [NSJSONSerialization JSONObjectWithData:self.responseData options:kNilOptions error:nil];
NSLog(#"%#", [recievedData description]);
}
#end
and the second one:
#import "ViewController.h"
#import "HTTPRequestHandler.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
HTTPRequestHandler *request = [[HTTPRequestHandler alloc] initWithURL:#"http://own-dev1.railwaymen.org:4006/api/get_grant_key"
body:#"email=vergun#gmail.com&password=password"];
[request makeConnectionWithRequest];
}
#end

Answer 1

Okey, got it! Just forgot self.responseData = [NSMutableData data];