Read through this snippet for a few minutes then walk us through what you think it does

permit.rb

class Permit < ActiveRecord::Base

  # ... snip*
  # Assume "def model" exists elsewhere in the class.

  def to_ability
    modes = [:create, :read, :update, :destroy].select do |mode| 
      self.send(:"can_#{mode}?")
    end

    object = model

    unless self[:model_id].nil?
      if object.is_a? Register
        model_id = self[:model_id]
      else
        model_id = self[:model_id].to_i # ActiveRecord doesn't like string ids
      end
      options = {:id => model_id }
      object = object.class
    end

    return [modes, object, options || {}]
  end

  # ... snip*

end