Module: SknUtils::Configurable

Defined in:
lib/skn_utils/configurable.rb

Overview

In the end, we have got ourselves a pretty neat module for making an arbitrary class configurable and then specifying those configuration values using a clean and simple DSL that also lets us reference one configuration attribute from another:

Inside Target component

class MyApp

include SknUtils::Configurable.with(:app_id, :title, :cookie_name)
# ...

end

Inside Initializer

MyApp.configure do

app_id "my_app"
title "My App"
cookie_name { "#{app_id}_session" }

end

Usage:

MyApp.config.app_id # ==> “my_app”

Here is the final version of the module that implements our DSL—a total of 36 lines of code:

Class Method Summary collapse

Class Method Details

.with(*attrs) ⇒ Object 



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# File 'lib/skn_utils/configurable.rb', line 39

def self.with(*attrs)
  not_provided = Object.new

  # Define the class/module methods
  config_class = Class.new do
    attrs.each do |attr|
      define_method attr do |value = not_provided, &block|
        if value === not_provided && block.nil?
          result = instance_variable_get("@#{attr}")
          result.is_a?(Proc) ? instance_eval(&result) : result
        else
          instance_variable_set("@#{attr}", block || value)
        end
      end
    end

    attr_writer *attrs
   end

  # Define the runtime access methods
  class_methods = Module.new do
    define_method :config do
      @config ||= config_class.new
    end

    def configure(&block)
      config.instance_eval(&block)
    end
  end

  # Apply the custom configuration
  Module.new do
    singleton_class.send :define_method, :included do |host_class|
      host_class.extend class_methods
    end
  end

end