class_methods

Define class methods from given block. You can define private class methods as well.

module Example
  extend ActiveSupport::Concern

  class_methods do
    def foo; puts 'foo'; end

    private
      def bar; puts 'bar'; end
  end
end

class Buzz
  include Example
end

Buzz.foo # => "foo"
Buzz.bar # => private method 'bar' called for Buzz:Class(NoMethodError)