env_vars: Access environment variables. Also includes presence validation, type coercion and default values.

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Add this line to your application's Gemfile:

gem "env_vars"

And then execute:

$ bundle

Or install it yourself as:

$ gem install env_vars


Config = Env::Vars.new do
  mandatory :database_url, string
  optional  :timeout, int, 10
  optional  :force_ssl, bool, false
  optional  :rails_env, "development", string, aliases: %w[env]


If you're going to use env_vars as your main configuration object, you can also set arbitrary properties, like the following:

Config = Env::Vars.new do
  optional :redis_url, string, "redis://"
  property :redis, -> { Redis.new } # pass an object that responds to #call
  property(:now) { Time.now }       # or pass a block.

Config.redis.set("key", "value")
#=> "value"

Values are cached by default. If you want to dynamically generate new values, set cache: false.

Config = Env::Vars.new do
  property(:uuid, cache: false) { SecureRandom.uuid }


You can coerce values to the following types:

  • string: Is the default. E.g. optional :name, string.
  • int: E.g. optional :timeout, int.
  • float: E.g. optional :wait, float.
  • bigdecimal: E.g. optional :fee, bigdecimal.
  • bool: E.g. optional :force_ssl, bool. Any of yes, true or 1 is considered as true. Any other value will be coerced to false.
  • symbol: E.g. optional :app_name, symbol.
  • array: E.g. optional :chars, array or optional :numbers, array(int). The environment variable must be something like a,b,c.

Dotenv integration

If you're using dotenv, you can simply require env_vars/dotenv. This will load environment variables from .env.local.%{environment}, .env.local, .env.%{environment} and .env files, respectively. You must add dotenv to your Gemfile.

require "env_vars/dotenv"

Configuring Rails

If you want to use env_vars even on your Rails configuration files like database.yml and secrets.yml, you must load it from config/boot.rb, right after setting up Bundler.

ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile", __FILE__)

# Set up gems listed in the Gemfile.
require "bundler/setup"

# Load configuration.
require "env_vars/dotenv"
require File.expand_path("../config", __FILE__)


After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.


Bug reports and pull requests are welcome on GitHub at https://github.com/fnando/env_vars. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.


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