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 1️⃣Follows 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 (
📖Read more about the motivation in the Wrapping JSON-based ActiveRecord attributes with classes post
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.
Register the field in the ActiveRecord model class:
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 re-assigned; Rails doesn't track mutations of objects. For example:
self.my_stored_models = my_stored_models.map(&:as_json)
- StoreModel::Model API:
Initially sponsored by Evil Martians.
The gem is available as open source under the terms of the MIT License.