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)