ExState loads and persists workflow execution to a database through Ecto.

The ExState.Execution is built through the subject's :workflow association.

Setup

defmodule ShipmentWorkflow do
  use ExState.Definition

  workflow "shipment" do
    subject :shipment, Shipment

    initial_state :preparing

    state :preparing do
      state :packing do
        on :packed, :sealing
      end

      state :sealing do
        on :unpack, :packing
        on :sealed, :sealed
      end

      state :sealed do
        final
      end

      on_final :shipping
    end

    state :shipping do
      on :shipped, :in_transit
    end

    state :in_transit do
      on :arrival, :arrived
    end

    state :arrived od
      on :accepted, :complete
      on :return, :returning
    end

    state :returning do
      on :arrival, :returned
    end

    state :returned do
      on :replace, :preparing
    end

    state :complete do
      final
    end
  end
end

defmodule Shipment do
  use Ecto.Schema
  use ExState.Ecto.Subject

  schema "shipments" do
    has_workflow ShipmentWorkflow
  end
end

Creating

sale = %Sale{id: 1}

execution = ExState.create(sale) #=> %ExState.Execution{}

Updating

sale = %Sale{id: 1}

{:ok, sale} =
  sale
  |> ExState.load()
  |> ExState.Execution.transition!(:packed)
  |> ExState.Execution.transition!(:sealed)
  |> ExState.persist()

sale.workflow.state #=> "shipping"

{:error, reason} = ExState.transition(sale, :return)
reason #=> "no transition from state shipping for event :return"