Class Macros

finders.rb

module Finders
  def find_by(*attributes)
    attributes.each do |attribute|
      define_method("find_by_#{attribute}") do |criteria|
        puts "Finding by #{attribute} with #{criteria}"
        all.find{|c| c.send(attribute).to_s == criteria.to_s}
      end
    end
  end
end

class MerchantRepository
  # include or extend
  # include it means you want instance methods
  # ^                         ^
  # extend makes class methods
  extend Finders

  find_by :id, :name, :created_at, :updated_at

  def all
    []
  end

end

class CustomerRepository
  extend Finders

  find_by :id, :first_name, :last_name, :created_at, :updated_at

  def all
    []
  end

end

repo = CustomerRepository.new
repo.find_by_id("1")