WorkflowToHash

A tool to allow a sequence of actions in a state machine to be defined as an array.

Installation

Add this line to your application's Gemfile:

gem 'workflow_to_hash'

And then execute:

$ bundle

Or install it yourself as:

$ gem install workflow_to_hash

Usage

This tool has been specifically designed to work with Piotr Murach's FiniteMachine but is not limited to that environment.

When building state matchines, I regularly find that state needs to move in a sequence of steps. For example, :one to :two to three. In FiniteMachine, to achieve that you can do this:

require 'finite_machine'
class StateMachine < FiniteMachine::Definition
  initial :one

  events {
    event(
      :next,
      :one => :two,
      :two => :three
    )
  }
end

sm = StateMachine.new
sm.state # --> :one
sm.next
sm.state # --> :two
sm.next
sm.state # --> :three

That is OK, but gets a little unwieldy as the sequence grows or when you want to swap out sequences depending on a condition.

WorkflowToHash allow me to create state sequences more easily. For example, to achieve the above I could:

require 'finite_machine'
require 'workflow_to_hash'

class Workflow < WorkflowToHash::Workflow
  def forward
    [:start, :one, :two, :three]
  end

  def backward
    [:start, :three, :two, :one]
  end
end

class StateMachine < FiniteMachine::Definition
  initial :start

  events {
    event(
      :next,
      Workflow.for(:forward)
    )
  }
end

sm = StateMachine.new
sm.state # --> :start
sm.next
sm.state # --> :one
sm.next
sm.state # --> :two
sm.next
sm.state # --> :three

And then it allows me to build more complex state machines succinctly:

class StateMachine < FiniteMachine::Definition
  initial :start

  events {
    event(
      :next,
      Workflow.for(:forward).merge(if: -> {target.forward})
    )
    event(
      :next,
      Workflow.for(:backward).merge(if: -> {!target.forward})
    )
  }
end

require 'ostruct'
forward = OpenStruct.new forward: true
backward = OpenStruct.new forward: false

sm = StateMachine.new
sm.target forward
sm.state # --> :start
sm.next
sm.state # --> :one
sm.next
sm.state # --> :two
sm.next
sm.state # --> :three

sm = StateMachine.new
sm.target backward
sm.state # --> :start
sm.next
sm.state # --> :three
sm.next
sm.state # --> :two
sm.next
sm.state # --> :one

Development

Run rake test 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.

Contributing

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

License

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