Declarative transaction in Rails #ginzarb

When talking about declarative transactions at Ginza Ruby Conference 01, @a_matsuda doesn't want Rails to have declarative transactions? I was saying something like that, so I made it quickly with gem.

https://github.com/ttanimichi/transactional

What is a declarative transaction?

A declarative transaction is a method of declaratively describing that a transaction is automatically executed when a method is called. Java's Spring Framework is a well-known implementation framework. For Spring Framework, you can use declarative transactions by annotating methods with @Transactional.

@Transactional
public void create(int id) {
    // do something
}

How to use

Add it to your Gemfile and do a bundle install.

gem 'transactional'

All you have to do now is specify in transactional the action you want to make a transaction with in Controller.

class YourController < ApplicationController
+  transactional :create, :update
+
  def index
  end

  def create
    Post.create!(name: 'john', age: 42)
    Topic.create!(title: 'invalid title')
    render plain: :created
  end

  def update
  end
end

Will automatically take a transaction when the specified action is called.

Processing by YourController#create as HTML
   (0.2ms)  BEGIN
  SQL (0.5ms)  INSERT INTO "posts" ("name", "age", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id"  [["name", "john"], ["age", 42], ["created_at", "2017-08-06 08:23:13.980493"], ["updated_at", "2017-08-06 08:23:13.980493"]]
   (0.2ms)  ROLLBACK

In this example, you can see that the posts INSERT is rolled back when Topic's create! Throws an exception.