ROR : Workflow gem : I want to implement dynamic states from database

问题

I am currrently working on a project that has to implement dynamic workflow.

Dynamic: I store workflow's states in database table called wf_steps and the workflow gem has to create states for a particular workflow from the database

For that I am trying to use the workflow gem. You can see how it initializes states and corresponding events in the gem's github-page.

My code:

class SpsWorkflow < ActiveRecord::Base
  belongs_to :user
  has_many :wf_steps
  include Workflow
  workflow do
    # binding.pry
    # read wf-states from the database
    # for now let event be same for all the states
    self.wf_steps.each do |step|
      state step.title.to_sym do
        event :assign, transitions_to: :assigning
        event :hire, transitions_to: :hiring
        event :not_hire, transitions_to: :not_hiring
      end
    end
  end
end

Expectation and Problem encountered:

I expected in the code block below the term self.wf_steps would return my SpsWorkflow's instance/collection. However the self keyword returns #<Workflow::Specification:0x000000063e23e8 @meta={}, @states={}> when I use binding.pry inside the workflow method's block ( I commented in the code )

# read wf-states from the database
# for now let event be same for all the states
  self.wf_steps.each do |step|
    state step.title.to_sym do

Need you help, thanks

EDIT: I also tried storing the instance in a variable and using the variable inside the block passing to the workflow method call.

class SpsWorkflow < ActiveRecord::Base
  include Workflow
  sps_instance = self

But I got the instance of the class SpsWorkflow like

SpsWorkflow(id: integer, workflow_state: string, assigned_to: integer, title: string, description: string, organization_id: integer, user_id: integer, created_at: datetime, updated_at: datetime)

but I want

 #<SpsWorkflow id: 1, workflow_state: "step1", assigned_to: nil, title: "Software Engineer", description: "Hire best engineer", organization_id: nil, user_id: 1, created_at: "2015-08-08 00:58:12", updated_at: "2015-08-08 00:58:12">

回答1:

You have used:

workflow do
  self.something
end

self in the context of this block will refer to the WorkflowSpecification. If you really want access to the instance of SpsWorkflow, you may have to pass it into the block or assign it to a different variable and use it there.

回答2:

I finally solved it using a activerecord callback

class SpsWorkflow < ActiveRecord::Base
  include Workflow
  after_initialize do
    sps_instance = self
    SpsWorkflow.workflow do
      # read wf-states as well as events from the database
      sps_instance.wf_steps.each do |step|
        state step.title.to_sym do
          event :assign, transitions_to: :step2
          event :hire, transitions_to: :hire
          event :not_hire, transitions_to: :not_hiring
        end
      end
    end
  end
  belongs_to :user
  has_many :wf_steps
end

来源：https://stackoverflow.com/questions/31911077/ror-workflow-gem-i-want-to-implement-dynamic-states-from-database

标签

ruby-on-rails

ruby

workflow

metaprogramming