Add this line to your application's Gemfile:

gem "superconfig"

And then execute:

$ bundle

Or install it yourself as:

$ gem install superconfig

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

Config.database_url
Config.timeout
Config.force_ssl?

You can specify the description for both mandatory and optional methods; this will be used in exceptions.

Config = SuperConfig.new do
  mandatory :missing_var, string, description: "this is important"
end

#=> SuperConfig::MissingEnvironmentVariable: MISSING_VAR (this is important) is not defined

If you're creating a library, you may want to use prefixed env vars. In this case, you can pass a prefix to SuperConfig.new.

Config = SuperConfig.new(prefix: "MYAPP") do
  optional :redis_url, string, "redis://127.0.0.1"
end

This will look for MYAPP_REDIS_URL in the environment variables.

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

Config = SuperConfig.new do
  optional :redis_url, string, "redis://127.0.0.1"
  property :redis, -> { Redis.new } # pass an object that responds to #call
  property(:now) { Time.now }       # or pass a block.
end

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

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

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

You can also set values using SuperConfig#set.

Config = SuperConfig.new do
  set :domain, "example.com"
end

You may want to start a debug session without raising exceptions for missing variables. In this case, just pass raise_exception: false instead to log error messages to $stderr. This is especially great with Rails' credentials command (rails credentials:edit) when already defined the configuration.

Config = SuperConfig.new(raise_exception: false) do
  mandatory :database_url, string, description: "the leader database"
end

#=> [SUPERCONFIG] DATABASE_URL (the leader database) is not defined

I like to centralize access to my Rails credentials; there's a handy mechanism for doing that with SuperConfig:

Config = SuperConfig.new do
  credential :api_secret_key
  credential :slack_oauth_credentials do |creds|
    SlackCredentials.new(creds)
  end
end

Config.api_secret_key
Config.slack_oauth_credentials
#=> The value stored under `Rails.application.credentials[:api_secret_key]`

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.
• json: E.g. mandatory :keyring, json. The environment variable must be parseable by JSON.parse(content).

Sometimes it gets hard to understand what's set and what's not. In this case, you can get a report by calling SuperConfig::Base#report. If you're using Rails, you can create a rake task like this:

# frozen_string_literal: true

desc "Show SuperConfig report"
task superconfig: [:environment] do
  puts YourAppNamespace::Config.report
end

Then, change your configuration so it doesn't raise an exception.

# frozen_string_literal: true
# file: config/config.rb

module YourAppNamespace
  Config = SuperConfig.new(raise_exception: false) do
    mandatory :database_url, string
    optional :app_name, string
    optional :wait, string
    optional :force_ssl, bool, true
  end
end

Finally, run the following command:

$ rails superconfig
❌ DATABASE_URL is not set (mandatory)
✅ APP_NAME is set (optional)
⚠️ WAIT is not set (optional)
✅ FORCE_SSL is not set, but has default value (optional)

If you're using dotenv, you can simply require superconfig/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 "superconfig/dotenv"

If you want to use SuperConfig 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 "superconfig/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/superconfig. 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.

Icon made by eucalyp from Flaticon is licensed by Creative Commons BY 3.0.