StoreModel

StoreModel gem allows you to wrap JSON-backed DB columns with ActiveModel-like classes.

💪 Powered with Attributes API. You can use a number of familiar types or write your own
🔧 Works like ActiveModel. Validations, enums and nested attributes work very similar to APIs provided by Rails
1️⃣ Follows single responsibility principle. Keep the logic around the data stored in a JSON column separated from the model
👷‍♂️ Born in production.

class Configuration
  include StoreModel::Model

  attribute :model, :string
  enum :status, %i[active archived], default: :active

  validates :model, :status, presence: true
end

class Product < ApplicationRecord
  attribute :configuration, Configuration.to_type
end

Why should I wrap my JSON columns?

Imagine that you have a model Product with a jsonb column called configuration. This is how you likely gonna work with this column:

product = Product.find(params[:id])
if product.configuration["model"] == "spaceship"
  product.configuration["color"] = "red"
end
product.save

This approach works fine when you don't have a lot of keys with logic around them and just read the data. However, when you start working with that data more intensively–you may find the code a bit verbose and error-prone.

For instance, try to find a way to validate :model value to be required. Despite of the fact, that you'll have to write this validation by hand, it violates the single-responsibility principle: why parent model (Product) should know about the logic related to a child (Configuration)?

📖 Read more about the motivation in the Wrapping JSON-based ActiveRecord attributes with classes post

Getting started

Start with creating a class for representing the hash as an object:

class Configuration
  include StoreModel::Model

  attribute :model, :string
  attribute :color, :string
end

Attributes should be defined using Rails Attributes API. There is a number of types available out of the box, and you can always extend the type system.

class Product < ApplicationRecord
  attribute :configuration, Configuration.to_type
end

When you're done, the initial snippet could be rewritten in the following way:

product = Product.find(params[:id])
if product.configuration.model == "spaceship"
  product.configuration.color = "red"
end
product.save

Usage note: Rails and assigning Arrays/Hashes to records

Assigned attributes must be a String, Hash, Array of Hashes, or StoreModel. For example, if the attributes are coming from a controller, be sure to convert any ActionController::Parameters as needed.
Any changes made to a StoreModel instance requires the attribute be flagged as dirty, either by reassignment (self.my_stored_models = my_stored_models.map(&:as_json)) or by will_change! (self.my_stored_models_will_change!)
Mixing StoreModel::NestedAttributes into your model will allow you to use accepts_nested_attributes_for in the same way as ActiveRecord.

class Supplier < ActiveRecord::Base
  include StoreModel::NestedAttributes

  has_many :bicycles, dependent: :destroy

  attribute :products, Product.to_array_type

  accepts_nested_attributes_for :bicycles, :products, allow_destroy: true
end

This will allow the form builders to work their magic:

<%= form_with model: @supplier do |form| %>
  <%= form.fields_for :products do |product_fields| %>
    <%= product_fields.text_field :name %>
  <% end %>
<% end %>

Resulting in:

<input type="text" name="supplier[products_attributes][0][name]" id="supplier_products_attributes_0_name">

In the controller:

def create
  @supplier = Supplier.new(supplier_params)
  @supplier.save
end

private

def supplier_params
  params.require(:supplier).permit(products_attributes: [:name])
end

Documentation

Installation
StoreModel::Model API:

Credits

Initially sponsored by Evil Martians.

License