Here's a cheatsheet for a basic Rails backend:

1. Create a new Rails app as an api

I choose the database to be Postgres because it's easier to deploy.

• rails new <my_app_name> --database=postgresql --api
• cd to the new folder

2. Gemfile

• navigate to your Gemfile and uncomment gem 'rack-cors'
• also, add these: gem 'active_model_serializers', gem 'jwt' (if you're planning to do the auth) and gem 'activerecord-reset-pk-sequence'
• bundle install

3. CORS

Inside of config/initializers/cors.rb uncomment the following code:

Rails.application.config.middleware.insert_before 0, Rack::Cors do
  allow do
    origins '*'

    resource '*',
      headers: :any,
      methods: [:get, :post, :put, :patch, :delete, :options, :head]
  end
end

4. Models and validations

• draw domain model
• create models: rails g model User name:string age:integer account:belongs_to
  • remember to first generate the ones with has_many macros on them; then only the ones with belongs_to — this will be helpful when running migrations because otherwise you may get this error: ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR: relation "<some table name>" does not exist
• add appropriate associations on models (has_many and belongs_to, for instance)
• create migration: rails db:create
• run migration: rails db:migrate
• create validations
• in rails c try create a few instances, both correct and incorrect to test validations; then, test associations(e.g. User.all.first.laptop would check for the laptop of the first user and User.all.first.laptop.gadgets.first would check the first gadget that belongs to the laptop)

5. Routes

• in config/routes.rb specify the routes you'll be using
• since this is API, your routes should be placed in a namespace:

Rails.application.routes.draw do
  namespace :api do
      resources :users
      resources :questions, only: [:index, :show]
      resources :seen_questions, only: [:index, :show, :create]
      resources :question_categories, only: [:index, :show]
  end
end

• if you want to add versioning, this is the syntax:

Rails.application.routes.draw do
  namespace :api do
    namespace :v1 do
      resources :users
      resources :questions, only: [:index, :show]
      resources :seen_questions, only: [:index, :show, :create]
      resources :question_categories, only: [:index, :show]
    end
  end
end

6. Controllers

• create controllers with rails g controller api/v1/Users
• add appropriate actions

7. Serializers

• create serializers with rails g serializer post
• note: serializers can take custom methods or a macro has_many

8. Seed data

• at the top write SomeClassName.destroy_all for each of the classes; start with the ones that belongs_to and only afterwards, add those that has_many — this will allow you to avoid multiplications in your database when you run rails db:seed again;
• afterwards, write in the same sequence SomeClassName.reset_pk_sequence —- this will allow you to always start fresh ids whenever you run rails db:seed;
• see if everything is showing well on your endpoints