SimpleServiceObject

A simple command pattern implementation in Ruby.

Installation

Add this line to your application's Gemfile:

gem 'simple_service_object'

And then execute:

$ bundle

Or install it yourself as:

$ gem install simple_service_object

Usage

Basic usage

Write your service object class, which must inherit from SimpleServiceObject::Base and must define a call instance method.

  class SubscribeUser < SimpleServiceObject::Base
    def initialize(user)
      @user = user
    end

    def call
      add_user_to_newsletter_recipients(@user)
      notify_user(@user)
    end

    private

    def add_user_to_newsletter_recipients(user)
      # ...
    end

    def notify_user(user)
      # ...
    end
  end

To run your command, simply:

  SubscribeUser.call(my_new_user) # arguments are passed to your class '#initialize' method

Return value and errors

You can add errors using the errors method, which exposes to you an array of errors.

class CalculateSquareRoot < SimpleServiceObject::Base
  def initialize(number)
    @number = number
  end

  def call
    if number < 0
      errors.push("Cannot calculate square root!")
      return
    end
    Math.sqrt(@number)
  end
end

  result = CalculateSquareRoot.call(9)
  result.success? # true
  result.failure? # false
  result.errors # []
  result.value # 3.0

  result = CalculateSquareRoot.call(-1)
  result.success? # false
  result.failure? # true
  result.errors # ["Cannot calculate square root!"]
  result.value # nil

You can also use .call! instead of .call. If there aren't any errors, it will return the value, otherwise it will raise an exception.

  CalculateSquareRoot.call!(9) # 3.0
  CalculateSquareRoot.call!(-1) # raises SimpleServiceObject::FailureError

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake to run rubocop and 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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/welaika/simple_service_object. 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.

License

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