dry-system 0.21

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Settings

Basic usage

dry-system provides a built-in :settings component which you can use in your application. In order to set it up, simply define a bootable :settings component and import it from the :system provider:

# in system/boot/settings.rb
require "dry/system/components"
require "path/to/dry/types/file"

Application.boot(:settings, from: :system) do
  settings do
    key :database_url, Types::String.constrained(filled: true)
    key :logger_level, Types::Symbol.constructor { |value| value.to_s.downcase.to_sym }
                                    .default(:info)
                                    .enum(:trace, :unknown, :error, :fatal, :warn, :info, :debug)
  end
end

Now, dry-system will map values from ENV variable to settings struct and allows you to use it in the application:

Application[:settings] # => dry-struct object with settings

You can also use settings object in other bootable dependencies:

Application.boot(:redis) do |container|
  init do
    use :settings

    uri = URI.parse(container[:settings].redis_url)
    redis = Redis.new(host: uri.host, port: uri.port, password: uri.password)

    container.register('persistance.redis', redis)
  end
end

Or use :settings as an injectible dependency in your classes:

  module Operations
    class CreateUser
      include Import[:settings, :repository]

      def call(id:)
        settings # => dry-struct object with settings

        # ...
      end
    end
  end
end

Default values

You can use dry-types for provide default value for specific setting:

settings do
  key :redis_url, Types::Coercible::String.default('')
end

In this case, if you don't have ENV['REDIS_URL'] value, you get '' as the default value for settings.redis_url calls.

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