Configurable Ruby Modules: The Module Builder Pattern

wrapper.rb

module Wrapper
  InstanceMethods = Module.new

  def self.for(klass, accessor_name: nil)
    InstanceMethods.module_eval do
      define_method :initialize do |object|
        raise TypeError, "not a #{klass}" unless object.is_a?(klass)
        @object = object
      end

      method_name = accessor_name || begin
        klass_name = klass.to_s.gsub(/(.)([A-Z])/, '\1_\2').downcase
        "original_#{klass_name}"
      end

      define_method(method_name) { @object }
    end

    InstanceMethods
  end
end

class IntWrapper
  include Wrapper.for(Integer)
end

class StringWrapper
  include Wrapper.for(String)
end

IntWrapper.new(1).original_integer
# TypeError: not a String
# from (pry):7:in `block (2 levels) in for'

module Wrapper
  def self.for(klass, accessor_name: nil)
    mod = const_set("#{klass}InstanceMethods", Module.new)

    mod.module_eval do
      define_method :initialize do |object|
        raise TypeError, "not a #{klass}" unless object.is_a?(klass)
        @object = object
      end

      method_name = accessor_name || begin
        klass_name = klass.to_s.gsub(/(.)([A-Z])/, '\1_\2').downcase
        "original_#{klass_name}"
      end

      define_method(method_name) { @object }
    end

    mod
  end
end

class IntWrapper
  include Wrapper.for(Integer)
end

class StringWrapper
  include Wrapper.for(String)
end