-JSONValue failed. Error is: Unexpected end of input
===

I got the JSON result = -JSONValue failed. Error is: Unexpected end of input. please direct me in right way.

I am new in parsing . I have to get Data from the server by POST method. I have following details. I have to pass zip with url


    {"zip":"52435","methodIdentifier":"search_dealer"}

    url : http://usaautoleads.com/api.php

    method: post

    web service name: search_dealer

    response : {"success":"0","dealer":[info...]}

my code is here. 


      NSURL *myURL=[NSURL URLWithString:@"http://usaautoleads.com/api.php"];
    
  
    NSString *post =[[NSString alloc]initWithString:@"52435"];
    
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
    
    NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
    
    [request setURL:myURL]; 

    [request setHTTPMethod:@"POST"];

    [request setHTTPBody:postData]; 

    [request setValue:@"application/json" forHTTPHeaderField:@"content-type"];

    
     [[NSURLConnection alloc] initWithRequest:request delegate:self];

