title: How to add default array to column in db
body: <p>Now i am trying add default value to database column. I am trying with the following migration file. </p>
  
  <pre><code>def change
    add_column :user_preferences, :preference, :default =&gt; "Media, Responsibilities, Email"
  end
  </code></pre>
  
  <p>When i am trying to <code>rake db:migrate</code> it show the following error.</p>
  
  <pre><code>undefined method `to_sym' for #&lt;Hash:0x007fc33683e658&gt;/db/migrate/20141120090990_add_preference_to_user_preference.rb:3:in `change'
  NoMethodError: undefined method `to_sym' for #&lt;Hash:0x007fc33683e658&gt;
  /db/migrate/20141120090990_add_preference_to_user_preference.rb:3:in `change'
  </code></pre>
  
  <p>In model </p>
  
  <p><code>serialize :preference</code></p>
  
  <p>I want to add default to that <code>preference</code> column. Help me.</p>