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DSL for building class initializer with params and options.


Add this line to your application's Gemfile:

gem 'dry-initializer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install dry-initializer


require 'dry-initializer'
require 'dry-types'

class User
  extend Dry::Initializer::Mixin

  # Params of the initializer along with corresponding readers
  param  :name,  type: Dry::Types["strict.string"]
  param  :role,  default: proc { 'customer' }
  # Options of the initializer along with corresponding readers
  option :admin, default: proc { false }
  option :vip,   optional: true

# Defines the initializer with params and options
user = User.new 'Vladimir', 'admin', admin: true

# Defines readers for single attributes
user.name  # => 'Vladimir'
user.role  # => 'admin'
user.admin # => true
user.vip   # => Dry::Initializer::UNDEFINED

See full documentation on the Dry project official site


The dry-initializer is pretty fast for rubies 2.2+ comparing to other libraries.


Tested under rubies compatible to MRI 2.2+.


  • Fork the project
  • Create your feature branch (git checkout -b my-new-feature)
  • Add tests for it
  • Commit your changes (git commit -am '[UPDATE] Add some feature')
  • Push to the branch (git push origin my-new-feature)
  • Create a new Pull Request


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