How to integrate AASM (ActsAsStateMachine) in Ruby on Rails
Ruby on Rails provides a powerful framework for building web applications, and one essential aspect of many applications is managing the state of objects. AASM, or ActsAsStateMachine, is a Ruby library that makes it seamless to implement state machines in our Rails models. In this answer, we will explore the process of integrating AASM into our Ruby on Rails application and demonstrate how it can simplify state management.
Note: A sample application is provided in the demo example at the end of this Answer.
Installation
To get started, we add the AASM gem to our Rails application by including it in our Gemfile:
gem 'aasm'
Then, we run bundle install in our terminal.
Usage
Let’s illustrate the integration process by considering a common scenario: managing the state of resumes in a job application system. Assume we have a Resume model, and we want to track whether a resume is pending, accepted, or rejected.
1. Generating a migration
We start by generating a migration to add a state column to the resumes table:
rails generate migration AddStateToResumes state:string
We run the migration using the following command:
rails db:migrate
2. Including AASM in the model
We open the Resume model (usually located in ./app/models/resume.rb) and include AASM:
class Resume < ApplicationRecordinclude AASMaasm column: 'state' dostate :pending, initial: truestate :acceptedstate :rejectedevent :accept dotransitions from: :pending, to: :acceptedendevent :reject dotransitions from: :pending, to: :rejectedendendend
In this example, we define three states (pending, accepted, and rejected) and two events (accept and reject) to transition between them.
3. Handling states in the controller
We add the following two new actions to the ResumesController (usually located in ./app/controllers/resumes_controller.rb):
accept: To handle the functionality if the resume is accepted.reject: To handle the functionality if the resume is rejected.
These actions look like the following:
def accept@resume = Resume.find(params[:id])@resume.accept!redirect_to resumes_pathenddef reject@resume = Resume.find(params[:id])@resume.reject!redirect_to resumes_pathend
4. Updating the view
Let’s update the views to display resumes and allow state transitions using buttons. In the ./app/views/resumes/index.html.erb file, we include the following code:
<div class="container"><h1>Resumes</h1><table class="table table-striped table-bordered"><thead><tr><th>Name</th><th>State</th><th>Actions</th></tr></thead><tbody><% @resumes.each do |resume| %><tr><td><%= resume.name %></td><td><%= resume.state %></td><td><% if resume.pending? %><%= button_to 'Accept', accept_resume_path(resume), method: :put, class: 'btn btn-success' %><%= button_to 'Reject', reject_resume_path(resume), method: :put, class: 'btn btn-danger' %><% else %>No action required!<% end %></td></tr><% end %></tbody></table><%= link_to 'New Resume', new_resume_path, class: 'btn btn-primary' %></div>
Assuming we have already added Bootstrap to the application, the above-mentioned code will display the resumes in the form of a table with two buttons, “Accept” and “Reject,” for each resume to change its state.
5. Adding routes for the states
Lastly, we’ll add some routes to our application to handle the accept and reject actions. We add the following code to the config/routes.rb file in the Rails.application.routes.draw block:
resources :resumes domember doput :acceptput :rejectendend
Conclusion
Integrating AASM into our Ruby on Rails application provides an elegant solution for managing the state of our models. By defining states and transitions, we can bring clarity and structure to complex workflows. AASM’s straightforward syntax and seamless integration with Rails make it a valuable tool for developers working on applications with dynamic state requirements.
In summary, AASM simplifies state management in Ruby on Rails, allowing us to focus on building robust and maintainable applications. By incorporating AASM into our project, we empower our models with a powerful state machine that enhances the overall flexibility and efficiency of our application.
Demo example
Go through the demo application provided below. Start the Rails server by clicking the “Run” button. By default, the /resumes page is visible on the output. You can also view your application by clicking on the link provided next to “Your app can be found at:”.
Click the “New Resume” button, provide a name in the form, and click the “Create Resume” button. After successfully creating the resume, click the “Back to resumes” button. It’ll display the “Accept” and “Reject” buttons with that particular resume.
Click any of the buttons to transition its state.
Note: You might need to refresh the page to see the updated changes.
# This file is used by Rack-based servers to start the application. require_relative "config/environment" run Rails.application Rails.application.load_server
