Mechanical

Simple gem which allows to store multiple models in a single table in DB (Postgres only). It's using STI and Postgres JSONB data type.

The whole schema is defined in one initializer file, and new attributes could be easily added just by adding new attribute in that file. So you don't need to create a migration.

Usage

• add in the Gemfile gem "mechanical"
• execute bundle install
• execute rails g mechanical initializer
• execute rake db:migrate
• edit config/initializers/mechanical.rb and define your schema
• start app rails s
• you can use models Mechanical::Model::MODEL_NAME in you app like a regular model.

You need to define attribute and it's type (it's importan to check this gem: https://github.com/madeintandem/jsonb_accessor). In addition you can specify relations, validations, add instance or class methods. Behavior is the same as with AR model.

Mechanical.setup do |config|

  model "Account" do
    field :name, type: :string
    field :balance, type: :integer

    has_many :posts

    validates :name, presence: true
    validates :balance, numericality: true
  end

  model "Post" do
    field :title, type: :string
    field :description, type: :text
    field :published_on, type: :date
    field :account_id, type: :integer
    field :active, type: :boolean, default: true

    belongs_to :account, optional: true

    has_one_attached :file

    validates :title, presence: true

    scope :active, -> { jsonb_where(:mechanical_data, active: true) }

    after_create :say_hello

    add_methods do
      def self.total_posts
        self.count
      end

      def title_uppercase
        title&.upcase
      end

      def say_hello
        puts "HELLO FROM initializer #{self}"
      end
    end
  end

end

After Installation you can do the following:

  post = Mechanical::Model::Post.create(title: "Hello world", description: "this is description")
  post.persisted? # true

  post.title # "Hello world"
  post.description # "this is description"

  # for querying use: https://github.com/madeintandem/jsonb_accessor

  Mechanical::Model::Post.create(title: "ABC", description: "this is description")
  Mechanical::Model::Post.create(title: "TRE", description: "this is second description")
  Mechanical::Model::Account.create(name: "XYZ", balance: 100)
  Mechanical::Model::Account.create(name: "MTR", balance: 200)
  Mechanical::Model::Post.jsonb_where(:mechanical_data, { title: 'ABC' }).count # 1
  Mechanical::Model::Account.mechanical_data_where(balance: { greater_than_or_equal_to: 150 }).count # 1
  Mechanical::Model::Account.mechanical_data_where(balance: 10..250).count # 2

If you are building form and want to use this model you can do it same way as using regular model:

Example of very simple controller:

  def index
    @post  = Mechanical::Model::Post.new
  end

  def submit_post
    @post = Mechanical::Model::Post.new(params.require(:post).permit!)
    @post.user = User.first
    @post.save
    if @post.save
      redirect_to root_path
    else
      @posts = Mechanical::Model::Post.all
      render :index
    end
  end

View:

<%= simple_form_for @post, url: submit_post_url, html: { novalidate: true } do |f| %>
  <%= f.error_messages %>
  <%= f.association :account %>
  <%= f.input :title %>
  <%= f.input :description %>
  <%= f.input :published_on %>
  <%= f.input :file %>
  <%= f.input :active %>
  <br/>
  <%= f.submit %>
<% end %>

As you can see it supports active storage.

Installation

Add this line to your application's Gemfile:

gem 'mechanical'

And then execute:

$ bundle

Contributing

You are welcome to contribute.

License

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