An example for dynamic configuration loading in ruby (using json)

conf.json

{
  "key1": "string",
  "key2": true,
  "key3": 10,
  "nested": {
    "nested_key1": [1]
  }
}

conf.rb

require 'json'

class Conf

  def initialize(file, opts={symbolize_names: true})
    @file = file
    @options = opts

    load_file
  end


  def load_file
    @json = JSON.parse(open(@file).read, @options)
  end

  def get(key, default='')
      @json[key] || default
  end


  def method_missing(method_sym, *arguments)
    case method_sym.to_s
    when /^get_nested(.*?)$/
     # todo
    when /^get_(.*?)$/
      key = $1
      key = key.to_sym if @options[:symbolize_names] == true
      self.get(key,(arguments.first || ''))
    else
      super
    end
  end

  def respond_to?(method, include_private = false)
    if method.to_s =~ /^get_.*?$/
      true
    else
      super
    end
  end

end

usage:
conf = Conf.new('conf.json')
conf.get_key1 'default value'