the %Q{..} doesn't show the iframe. The html dom is being displayed on the view.

post controller

def youtube_embed(youtube_url)
  if youtube_url[/youtu\.be\/([^\?]*)/]
    youtube_id = $1
  else
    # Regex from # http://stackoverflow.com/questions/3452546/javascript-regex-how-to-get-youtube-video-id-from-url/4811367#4811367
    youtube_url[/^.*((v\/)|(embed\/)|(watch\?))\??v?=?([^\&\?]*).*/]
    youtube_id = $5
  end

  %Q{<iframe title="YouTube video player" width="640" height="390" src="http://www.youtube.com/embed/#{ youtube_id }" frameborder="0" allowfullscreen></iframe>}
end

view

<p>
  <b>Name:</b>
  <%= @post.name %>
</p>

<p>
  <b>Link:</b>
  <%= @post.link %>
</p>


<%= youtube_embed(@post.link) %> <br/>