title: If record has user?
body: <p>Users have many cards and cards have many users, with a has_many through relationship.</p>
  
  <pre><code># card.rb
  has_many :card_assignments
  has_many :users, :through =&gt; :card_assignments
  
  # user.rb
  has_many :card_assignments
  has_many :cards, :through =&gt; :card_assignments
  
  # card_assignment.rb
  belongs_to :user
  belongs_to :card
  </code></pre>
  
  <p>In my view, I want to check if the current user is one of the users which belongs to the card, if that makes sense?</p>