how to pass an array as parameter when making a request to server,iphone
===

**Given** :

    a chunk of books and each book will associated with unique id

**Scenario** :

    user can order more than one book

**Goal** : 

       making an NSMutableURLRequest and send this request to server and let server know which books 
        are being picked 

**Question** :

      For example, user A will choose 3 books whose id are a, b ,c. How can I send an array 
      containing with these id in the request so that server can know that user A are ordering these books

