Introduction to Rails Service Objects

Introduction to Rails Service Objects

I won’t tell you what a service object is, there is a plethora of articles out there in the wild (web). Here I will show you how to make one yourself!

As we will be working today in rails there is a little bit of setup first ahead of us. If you already got some working rails project you can skip it and move to the service object part.

The setup

First of all we need a rails app so go ahead and fire up: rails new service_rails and hit enter cd into it and a quick scaffold to get started:

rails generate controller Articles

rails generate model Article

rake db:migrate

Now navigate to the /config/routes.rb and add a line: root 'articles#index' Open app/controllers/articles_controller.rb and add index method:

class ArticlesController < ApplicationController
  def index
    @articles = Article.all
  end
end

Next thing - the view. Navigate to the app/views/articles and touch index.html.erb In index file add some content, for example:

<h1>Articles</h1>

That’s it we are set up to make our first service object. If something above is not clear don’t worry here it is all covered. Now after hitting rails s you should see “Articles” heading from our view.

The service object.

Now the fun part. In the app folder let’s make another directory: mkdir prints and cd into it. Now let’s make our object: vim article_print.rb and hit enter. We want to make a method which prints greetings to the screen so:

class ArticlePrint
  def print_txt
    p "Greetings from the Service Object!"
  end
end

Can’t get simplier then this.

What’s next? We have to make it work somehere. Navigate to the article controller and add one line to index method:

class ArticlesController < ApplicationController
  def index
    @articles = Article.all
    @print = ArticlePrint.new.print_txt
  end
end

We are declaring a variable with print_txt method from ArticlePrint class (our service object)

Next step is display it somewhere, so let’s go to the index.html.erb in views/articles and add one line below our heading: <%= @print %>

It calls our variable from articles_controller file

That’s it - our first service object in rails. Go check it out by hitting rails s Of course it doesn’t do much but you could use service objects for much more sofisticated purposes with much, much more code inside them (and not in your models or controllers)

Cheers