title: if new news to make enabled, it is automatic removes enabled from the previous news
body: <p>If new news to make enabled, it is automatic removes enabled from the previous news.</p>
  
  <p>my callback:</p>
  
  <p>post.rb</p>
  
  <pre><code>after_update :removes_enabled
  
  def removes_enabled
    if enabled?
      self.enabled = false
    else
      self.enabled = true
    end
  end
  </code></pre>
  
  <p>admin/post.rb</p>
  
  <pre><code>column :enabled do |status|
    status.enabled? ? action_label = "Disable" : action_label = "Enable"
    link_to(action_label, status_admin_news_path(status), method: :put )
  end
  </code></pre>