title: ruby on rails - create and populate combobox / dropdown from another scaffold
body: <p>I want to display a combobox in my web page.<br>
  I have two objects :<br>
  i.e.<br>
    rails generate scaffold person id:integer name:string<br>
    rails generate scaffold state id:integer name:string  </p>
  
  <p>I want on the person to be able to choose state.<br>
  What is the best practice?<br>
  should I run a different scaffold ?<br>
  (one that will create me a foreign key in the db and another code ?)<br>
  thanks.</p>