gistfile1.builder

class Video < ActiveRecord::Base

  before_validation :set_attrs_via_embedly, :on => :create

  def set_attrs_via_embedly
    # example url: http://www.youtube.com/watch?v=oHg5SJYRHA0
    attrs = Embedly.get_attrs url
    errors[:base] << "is not a video" unless attrs['type'] == 'video'
    self.attributes = attrs
  end

end

gistfile2.builder

class Embedly

  def self.get_attrs(url)
    embedly_url = "http://api.embed.ly/v1/api/oembed?url=#{url}"
    response = RestClient.get embedly_url
    attrs = JSON.parse response.body
  rescue
    {}
  end

end