Trenchcoat

Install the gem and add to the application's Gemfile by executing:

$ bundle add trenchcoat

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install trenchcoat

Trenchcoat::Model is a concern that gives you some helper methods to streamline creating custom ActiveModels based on your existing models, which is great for building complex forms without making your ActiveRecord models a mess with virtual attributes.

Like 3 kids stacked on top of each other in a trenchcoat, your custom ActiveModel is quacking like your underlying model to sneak into the theater:

• There is a helper method to use the model attributes you want to fallback to if there is not already a value in this model
• It doesn't have any validations, it's just copying the attribute definitions you want from the model (that have corresponding ActiveModel types in your app).
• It delegates the model_name, id, and persisted? to make form helpers & persistence checks easier.

class Post < ApplicationRecord
  validates :body, presence: true
  validates :title, presence: true
end

# ...

class CustomForm
  include ActiveModel::Model
  include ActiveModel::Validations::Callbacks
  include ActiveModel::Attributes
  include Trenchcoat::Model

  attr_accessor :post

  copy_attribute_definitions(model_class: Post, attributes: %i[title body published_at])
  quack_like(model_instance_attr: :post)

  attribute :is_published, :boolean, default: false
  alias is_published? is_published

  before_validation :normalize_published_at

  def initialize(attributes = {})
    super

    published_at

    self.post = Post.new if post.blank?
    fallback_to_model_values(
      model: post,
      attributes_to_check: %i[title body published_at],
      original_attributes_hash: attributes
    )

    return if attributes.key?(:is_published)

    self.is_published = published_at.present?
  end

  def save!
    validate!

    post.update!(
      title: title,
      body: body,
      published_at: published_at
    )
  end

  protected

  def normalize_published_at
    unless is_published?
      self.published_at = nil
      return
    end

    return if published_at.present?

    self.published_at = Time.now
  end
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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.

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

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

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