gistfile1.txt

app/controllers/webhooks/versapay_controller.rb:

class Webhooks::VersapayController < ApplicationController
  check_versapay_signatures VERSAPAYSIGNINGKEY
  ...
end

from gem:

class ActionController::Base
  def self.check_versapay_signatures(key, *args)
    before_filter lambda { |controller| check_versapay_signature(key, controller)}, *args
    # before_filter lambda { |controller| ActionController::Base.check_versapay_signature(key, controller)}, *args
  end

  def self.check_versapay_signature(key, controller)
    ... 
    if all_is_good
      true
    else
      raise Versapay::InvalidWebhookSignature
    end
  end
end