Rails model templates, concept sketch

rails-model-templates.rb

require "active_record"
require "sqlite3"
require "minitest/autorun"
require "logger"
require "pp"

ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :devices, force: true do |t|
    t.string :name
    t.string :model
    t.string :location
    t.integer :year
  end

  create_table :interfaces, force: true do |t|
    t.integer :device_id
    t.string :name
    t.string :address
    t.boolean :enabled
  end

  create_table :templates, force: true do |t|
    t.string :name
    t.string :klass
    t.text :template
  end
end

class Template < ActiveRecord::Base
  def self.make!(object, name: default_name(object))
    create!(name: name, klass: object.class.to_s, template: object.as_template.to_json)
  end

  def use(&block)
    klass.constantize.from_template(JSON.parse(template), &block)
  end

  private
  def self.default_name(object)
    "New #{object.model_name.singular} template"
  end
end

class Device < ActiveRecord::Base
  has_many :interfaces

  def self.from_template(template, &block)
    if template.is_a?(Array)
      template.map { |tpl| from_template(tpl, &block) }
    else
      object = new(template.slice("model", "location", "year"), &block)
      object.interfaces << Interface.from_template(template["interfaces"])
      object
    end
  end

  def as_template
    {
      "model" => model,
      "location" => location,
      "year" => year,
      "interfaces" => interfaces.map(&:as_template)
    }
  end
end

class Interface < ActiveRecord::Base
  belongs_to :device

  def self.from_template(template, &block)
    if template.is_a?(Array)
      template.map { |tpl| from_template(tpl, &block) }
    else
      object = new(template.slice("name", "address", "enabled"), &block)
      object
    end
  end

  def as_template
    {
      "name" => name,
      "address" => address,
      "enabled" => enabled
    }
  end
end

class TemplateTest < Minitest::Test
  def test_template_stuff
    device = Device.create!(name: "router", model: "CX-6790", location: "SFO", year: 2017)
    device.interfaces << Interface.create!([{name: "de0", address: "10.0.0.1", enabled: false}, {name: "lo0", address: "127.0.0.1", enabled: true}])

    Template.make!(device, name: 'SFO router template')

    new_device = Template.last.use do |dev|
      dev.name = "router-2"
    end

    new_device.save!

    assert_equal 1, Template.count
    assert_equal 2, Device.count
    assert_equal 2, new_device.interfaces.count
    assert_equal new_device.id, Interface.last.device.id

    pp new_device.as_json(include: :interfaces)
  end
end