title: NSPredicate filter
body: <p>I have never used NSPredicate before so please bear with me. I have an array which have a boolean key as "isChecked". I want to filter the array which have the boolean set as "YES", any idea how can I do it, plus if there is any reference to such query methods that would be nice to have it handy.</p>
  
  <p>Thanks</p>