Using dry-configurable to store app settings.

settings.rb

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'dry-configurable'
end

require "singleton"

class Settings
  include Singleton
  extend Dry::Configurable

  # "reader: true" allows calling Settings.client_id instead of Settings.config.client_id
  setting :client_id, reader: true
  
  # "constructor: ..." allows doing some type coercion on the supplied value
  setting :redis_db, reader: true, constructor: ->(value) { Integer(value) }
  
  # "default: ..." allows to set some pre-defined default
  setting :coverband_enabled, reader: true, default: false, constructor: ->(value) { value == "true" }
  
  setting :foobar, reader: true
end

ENV["CLIENT_ID"] = "abc123"
ENV["REDIS_DB"] = "1"
ENV["COVERBAND_ENABLED"] = "true"

Settings.settings.map(&:name).each do |setting|
  value = ENV[setting.to_s.upcase]
  Settings.config.public_send("#{setting}=", value) if value
end

p Settings.client_id
# => "abc123"
p Settings.redis_db
# => 1
p Settings.coverband_enabled
# => true