Chief

A simple command pattern for Ruby.

Usage

A Chief::Command's primary interface is the .call method, executes the command and returns a Chief::Result instance.

A Chief::Result encapsulates whether the command succeeded, including the return values and (optionally) any errors encountered.

Suppose we have an ExampleApplication, that needs to notify an external service with a message. First, we create the command:

require 'net/http'

module ExampleApplication
  module SomeExternalService
    class Notify < Chief::Command
      attr_reader :message

      def initialize(message)
        @message = message
      end

      def call
        response = report_to_external_service

        if response.code == 200
          success!(message)
        else
          fail!(false, 'Could not notify the external service')
        end
      rescue => exception
        fail!(exception, 'Unexpected error while notifying service')
      end

      private

      def report_to_external_service
        Net::HTTP.post_form(
          URI.parse('https://some_external_service/messages'),
          message: message
        )
      end
    end
  end
end

You can use destructuring assignment to easily grab the value and the errors.

result, value, errors = ExampleApplication::SomeExternalService::Notify.call(message)

Things to consider

• A Chief::Command must call success! or fail!. We think this leads to better code so we enforce it.

irb(main):001:0> class ExampleCommand < Chief::Command
irb(main):002:1>   def call
irb(main):003:2>     nil
irb(main):004:2>   end
irb(main):005:1> end
=> :call
irb(main):006:0> ExampleCommand.call
RuntimeError: ExampleCommand must call success! or fail! and return the result
        from ../chief/lib/chief/command.rb:9:in `call'
        from (irb):6
        from bin/console:14:in `<main>'

Installation

Add this line to your application's Gemfile:

gem 'chief'

And then execute:

$ bundle

Or install it yourself as:

$ gem install chief

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the 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/policygenius/chief.

License

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