fresh_when

Sets the etag, last_modified, or both on the response and renders a "304 Not Modified" response if the request is already fresh.

Example:

  def show
    @article = Article.find(params[:id])
    fresh_when(:etag => @article, :last_modified => @article.created_at.utc)
  end

This will render the show template if the request isn’t sending a matching etag or If-Modified-Since header and just a "304 Not Modified" response if there’s a match.