how to integrate a captcha with devise at registration?

I assume there is some reasonably straightforwa开发者_如何学Pythonrd way to add Captcha to a rails3 app that's using Devise for authentication, but I cannot find any examples of how to 'connect' a captcha to the registration process.

I see several threads here on SO but they were discussing about the 'why' not the 'how'.

Any pointed would be helpful!

Take a look at the following guide, this has an implementation of reCAPTCHA:

https://github.com/plataformatec/devise/wiki/How-To:-Use-Recaptcha-with-Devise

  def create
    if method_to_check_captcha
      super
    else
      build_resource
      clean_up_passwords(resource)
      flash[:error] = "There was an error with the captcha code below. Please re-enter the code and click submit."
      render_with_scope :new
    end
  end

From there, just program the method to check the captcha.