title: How can I create relationships in multiple tables on rails?
body: <p>I'm new to rails and learning relationship between tables. This is what I want to create. Users wont be able to post into classes or videos just add them to their table.</p>
  
  <p>example: 
  I'm a student and I sign up for a user account. Then I choose the classes I want HTML and CSS. And then I'm only able to watch the videos inside those classes.</p>
  
  <pre><code>Users-&gt;classes-&gt;videos
  
  (USERS)
  username
  password
  classes - signs up for multiple classes
  
  (classes)
  HTML
  CSS
  Javascript
  PHP
  
  (inside of each class theres videos)
  video1
  video2
  video3
  </code></pre>