How to define service objects in Rails: the simple way

service.rb

# frozen_string_literal: true

class ApplicationService
  def self.call(...)
    new(...).call
  end

  def initialize(...)
  end
end

class CurrentIpService < ApplicationService
  def initialize(request)
    super

    @request = request
  end

  def call
    ip_headers = [
      @request.env["HTTP_CF_CONNECTING_IP"],
      @request.env["HTTP_CLIENT_IP"],
      @request.env["HTTP_X_FORWARDED_FOR"],
      @request.env["HTTP_X_FORWARDED"],
      @request.env["HTTP_FORWARDED_FOR"],
      @request.env["HTTP_FORWARDED"],
      @request.env["REMOTE_ADDR"]
    ]

    (ip_headers.find(&:present?) || "127.0.0.1").split(",").first
  end
end

CurrentIpService.call(request)

I use service objects in all of my Rails projects.

👷‍♂️ This is how I engineer them:

1. Define the ApplicationService class with the call class method that does nothing but accepts any params and initializes a service, then calls the call instance method immediately

2. Define the initialize instance method that does nothing but accepts any params

3. Define a service that inherits from ApplicationService and defines the call method. If a service requires params, I define the initialize method, call super, then use the params. If you don't need params, then you don't need to define initialize at all

4. Implement the call method.

That's all!

https://x.com/kyrylosilin/status/1820473128365019139