AR2DTO

AR2DTO (ActiveRecord to DTO, pronounced R2-D2 or Artoo-Detoo) is a gem that lets you create DTOs (data transfer objects) from your ActiveRecord models. It is a simple and small gem to encourage the usage of simpler objects across an app rather than ActiveRecord models, to help with coupling issues in large Rails apps.

Table of Contents

• Motivation
  • Why AR2DTO?
• Installation
• Usage
  • Global configuration
  • Setting up your models
  • DTO class
  • #to_dto
  • .to_dto
• Examples
• Development
• Contributing
• License
• Code of Conduct

Motivation

ActiveRecord is a very powerful tool and extensively used in most Rails apps. When working on large Rails apps, having such powerful objects all over the place can have a negative impact on the maintainability of the app. This is even more clear when trying to create domain boundaries within a Rails monolith. When there is communication between different components you probably don't want to share an ActiveRecord model with other components, if you do that, you'll be giving direct access to your component's tables from anywhere. For that reason, we want to create POROs that look like ActiveRecord models but that are much simpler and only carry data. This could be done by hand, but with this gem, we are trying to help you avoid having to write all the boilerplate to create these objects. As a corollary, by using this gem you are standardizing how things are done, and how your data-only objects look like.

Why AR2DTO?

• It lets you work with objects that are similar to ActiveRecord models but without DB access or business logic.
• It impedes ActiveRecord models leaking through its methods.
• It helps you reduce boilerplate.
• It provides a standard way to work with data-only objects.
• It is a very small gem focused on solving one specific problem.

Installation

Add this line to your application's Gemfile:

gem 'ar2dto'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install ar2dto

Usage

In the following sections, we explain the API provided by the gem and some basic usage.

Many aspects of AR2DTO are configurable for individual models; typically this is achieved by passing options to the has_dto method within a given model. Some aspects of AR2DTO are configured globally for all models.

Global Configuration

Global configuration options affect all threads and models where has_dto has been defined. A common place to put these settings is in a Rails initializer file such as config/initializers/ar2dto.rb. These settings are assigned directly on the AR2DTO.configure object.

Configuration options are:

• active_model_compliace: DTO objects behaves like ActiveModel objects to play well with other parts of Rails and its ecosystem. Defaults to true.
• except: array of attributes to exclude from the DTO. Defaults to [].
• delete_suffix: suffix to be delete from the model name. Defaults to nil.
• add_suffix: suffix to be added to the model name. Defaults to "DTO".

Syntax examples:

  # config/initializers/ar2dto.rb

  AR2DTO.configure do |config|
    config.active_model_compliance = true
    config.except = [:updated_at]
    config.delete_suffix = nil
    config.add_suffix = "DTO"
  end

OR

  # config/initializers/ar2dto.rb

  AR2DTO.configure.active_model_compliance = true
  AR2DTO.configure.except = [:updated_at]
  AR2DTO.configure.delete_suffix = nil
  AR2DTO.configure.add_suffix = "DTO"

These options are intended to be set only once, during app initialization.

Setting up your models

To use the gem, you need to add has_dto to your ActiveRecord models. For example:

class User < ApplicationRecord
  has_dto
end

This will dynamically create a class called UserDTO and will add two methods to your ActiveRecord model: #to_dto and .to_dto.

DTO class

This class is dynamically created based on your models that declare has_dto. The goal of these classes is to be data-only. They don't have access to the DB, business logic, or calculate things on the fly. They just store the data and provide them in a read-only fashion through plain simple methods.

In addition to that, and optionally, you can have these objects be compliant with the ActiveModel API, you can do that by configuring it globally with:

# config/initializers/ar2dto.rb

AR2DTO.configure do |config|
  config.active_model_compliance = true
end

With this, it'll be even easier to interchange ActiveRecord models for DTOs, because other parts of Rails and other gems will continue to work (e.g. Rails route helpers).

#to_dto

When calling #to_dto on an ActiveRecord model, a DTO object will be initialized with the model attributes. As an example:

user = User.create!(name: 'John', email: 'john@example.com')
user_dto = user.to_dto
# #<UserDTO:0x00007fab8ce66a10 @name="John" @email="john@example.com">

user_dto will be an instance of UserDTO and, by default, it will be initialized with the same attributes as the model, that is: id, name, email, created_at, and updated_at.

You can then use user_dto across your app, and even share it with other components, without having to worry about others making queries, modifying data, or even running business logic, where they shouldn't.

This method accepts the same options as ActiveRecord's #as_json, they are except, only, methods, and include.

except Excludes attributes from the model when creating the DTO.

only Selects the only attributes that should be included when creating the DTO.

methods Run methods defined in the model and stores the values into the DTO as attributes.

include Includes an association into the DTO. The association is also converted into a DTO in case of a has_one/belongs_to association, or into an Array of DTOs in case of a has_many association. The associations accepts the same options explained above.

.to_dto

This method is similar to #to_dto but meant for ActiveRecord::Relation. So that running:

User.last(10).to_dto

will return an Array consisting of 10 UserDTO. With this you are forcing the executing of the query, having collections of simple data objects, and avoiding other parts of the app from modifying the query.

It accepts the same options as #to_dto and uses them create each DTO.

⚠️ Warning! Given that this method executes the query and brings records into memory, you have to be careful when and how to use it. You may not want to bring all records from a large table into memory. Consider combining it with things such as pagination or batch processing.

Examples

If you want to look into examples of usages and configurations, you can find:

• Option methods examples
• Option except examples
• Option only examples
• Option include examples
• Option add_suffix and delete_suffix examples
• Option active_model_compliance examples
• Custom DTO examples

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/santib/ar2dto. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the AR2DTO project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.