README.md

N.B. The Bellroy technology team are transitioning away from Ruby as their primary programming language, and will not longer actively update this repository. Contact us if you'd like to take over as the primary maintainer.

Dry Monads Sorbet

Sorbet type hints for Dry::Monads.

This gem is very small, it opens up the Dry::Monads::Result and Dry::Monads::Maybe classes to add type members that are subsequently referred to in a bundled .rbi file for the dry-monads gem.

The bundled rbi annotations are installed/updated via a rake task included in the gem.

Installation

Add the gem to your Gemfile:

gem 'dry-monads-sorbet'

Copying the bundled RBI

You must copy in the bundled .rbi file that this gem maintains to add type annotations to your own project to type check your usage of Dry::Monads.

Following in the footsteps of sorbet-rails we've extracted this process to a rake task.

In a Rails project:

The rake task that copies the bundled .rbi files into your project should already be loaded. You can run it by entering:

bundle exec rake dry_monads_sorbet:update_rbi

Outside of Rails projects:

Include the Rakefile in your own projects Rakefile to get access to the rbi update command:

require 'dry-monads-sorbet'

spec = Gem::Specification.find_by_name 'dry-monads-sorbet'
rakefile = "#{spec.gem_dir}/lib/dry-monads-sorbet/Rakefile"
load rakefile

After including the Rakefile you should then have access to the task as described in the Rails project section.

Usage

Usage is fairly simple, just annotate your methods as follows:

require 'dry/monads/sorbet'

class MyLoginService
  extend T::Sig

  sig{params(username: String).returns(Dry::Monads::Result[StandardError, String])}
  def check_username(username)
    case username
    when 'samuelgiles93'
      Dry::Monads::Success('Hi Sam!')
    else
      Dry::Monads::Failure(
        StandardError.new('Unauthorised')
      )
    end
  end

  sig{params(username: String).returns(Dry::Monads::Maybe[Integer])}
  def find_fullname(username)
    case username
    when 'samuelgiles93'
      Dry::Monads::Some('Samuel Giles')
    else
      Dry::Monads::None()
    end
  end
end

With the type annotations in place you'll get type errors when you attempt to say call a method that doesn't exist on the Some of a Maybe or the Success of a Result.