title: get object from ComboBox
body: <p>Here is my problem.
  I have a generic class called FilteredComboBox that extends ComboBox. It is basically an editable combobox that filteres choices according to user input. This FilteredCombobox is feed by ObservableList of type Book, which is just a simple class with 2 fields, name and id (obviously it has getters, setters and toString).</p>
  
  <p>After user makes his choice and clicks on book that he wants from the dropdown, I would like to get  this book id by the method in book class called getBookId. Unfortunately when I say bookComboBox.getValue.getBookId I get cast exception, because getValue automatically calls toString method.
  Is there a way around it? I would like to make getValue() method to return an object of type book and just a\call my getBookId() from there.</p>
  
  <p>Any ideas?</p>