Simple configuration for Ruby.
Allows you to define configuration CONSTANTS that take values from environment variables. With support for default values, required variables and type conversions.
The are multiple ways of configuring your Rails application for different environments (e.g. staging, production, etc.). One of the popular ones is through environment variables. For example Heroku uses this type of configuration extensively.
One of the benefits of it is that configuration values are never stored in the source control system, which improves security (for sensitive configuration parameters) and also makes it easier to try different configuration setups w/o changing the sources or re-deploying the application.
On the other hand writing
(ENV['PRIMARY_DOMAIN'] || "myapp.com") every time
you need your domain string becomes cumbersome pretty fast, not to mention
duplication and having the default repeated all over the place.
A competent programmer will of course only do this once, and re-use the value everywhere. Something like this:
PRIMARY_DOMAIN = ENV['PRIMARY_DOMAIN'].presence || 'myapp.com' S3_BUCKET = ENV['S3_BUCKET'] || raise 'missing S3_BUCKET' ORDER_EXPIRATION_DAYS = (ENV['ORDER_EXPIRATION_DAYS'].presence || 1).to_i
But it quickly becomes complicated, and again, quite a bit of similarly looking code that begs to be refactored out.
This gem is something I extracted from a couple of my latest projects. It allows you to do just that, have a configuration parameters stored in constants with values coming from environment variables and ability to provide defaults or have required parameters (i.e. fail if missing).
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
$ gem install constfig
There is only one function provided by the gem:
With a default (optional variable)
You can call it with a default, like this:
define_config :DEFAULT_DOMAIN, "astrails.com"
In which case it will first look if
ENV['DEFAULT_DOMAIN'] is available, and
if not will use the 'astrails.com'. A constant
DEFAULT_DOMAIN will be
Without a default (required variable)
Or you can call it without the default:
In which case it will raise exception
ENV['DEFAULT_DOMAIN'] is not available.
Non-string variables are supported. If you provide a non-string default
(boolean, integer, float or symbol), the value that is coming from
be converted to the same type (using
to_symbol). For the
"1" will be treated as
anything else will be treated as
In the case of required variables, you can supply a
Class in place of the
default, and it will be used for the type conversion. Like this:
define_config :EXPIRATION_DAYS, Fixnum
For boolean variables you can supply either
There is a special case for
Array, e.i. when either default value is an array,
Array is passed as type. In this case the value is just passed to
This gem will not re-define existing constants, which can be used to define defaults for non-production environments.
Rails on Heroku
There is one caveat with Rails on Heroku. By default Heroku doesn't provide
environment variables to your application during the
stage of slug compilation. If you don't take care of it your application will
fail to compile its assets and might fail to work in production. To take care
of it you can either use Heroku Labs
option, or (and this is what I'd recommend) you can use development defaults
For example in Rails you con do this:
if Rails.env.development? || Rails.env.test? || ARGV.join =~ /assets:precompile/ DEFAULT_DOMAIN = 'myapp.dev' end define_config :DEFAULT_DOMAIN
In development and test environments it will use 'myapp.dev' ad
PRIMARY_DOMAIN, but in production and staging environment it will fail unless
PRIMARY_DOMAIN is provided by environment.
NOTE: make sure those configuration variables are not actually used for asset compilation. If they are, I'd go with
You can use the dotenv gem to manage your
- Fork it
- Create your feature branch (
git checkout -b my-new-feature)
- Commit your changes (
git commit -am 'Add some feature')
- Push to the branch (
git push origin my-new-feature)
- Create new Pull Request