Validation of objects inside array of jsonb objects with RubyOnRails

Question

How would you validate each object inside an array of object with Rails?

I am building a user profile form in our Rails app. Inside user model, we have basic string attributes but some jsonb fields as well. JSONb fields default to [] because we want to store an array of objects inside that attribute. Here is an example of simplified user model attributes:

• name: string
• email: string
• education: jsonb, default: []

Education is an array of objects such as:

[{
  school: 'Harvard university',
  degree: 'Computer Science',
  from_date: 'Tue, 11 Jul 2017 16:22:12 +0200`,
  to_date: 'Tue, 11 Jul 2017 16:22:12 +0200'
},{
  school: 'High school',
  degree: 'Whatever',
  from_date: 'Tue, 11 Jul 2017 16:22:12 +0200`,
  to_date: 'Tue, 11 Jul 2017 16:22:12 +0200'
}]

User should be able to click Add school button, to add more fields via jquery. That jquery part is not important for this question - maybe just an explanation why we used an Array of objects.

How would you validate each item in education array, so I can mark the text field containing validtion error with red color? I got adviced that using FormObject pattern might help here. I have also tried writing custom validator that inherits from ActiveModel::Validator class, but the main problem still lies in fact, that I am dealing with an array, not actual object..

Thanks for any constructive help.

Answer 1

You could treat education records as first-class citizens in your Rails model layer by introducing a non-database backed ActiveModel model class for them:

class Education
  include ActiveModel::Model

  attr_accessor :school, :degree, :from_date, :to_date

  validates :school, presence: true
  validates :degree, presence: true

  def initialize(**attrs)
    attrs.each do |attr, value|
      send("#{attr}=", value)
    end
  end

  def attributes
    [:school, :degree, :from_date, :to_date].inject({}) do |hash, attr|
      hash[attr] = send(attr)
      hash
    end
  end

  class ArraySerializer
    class << self
      def load(arr)
        arr.map do |item|
          Education.new(item)
        end
      end

      def dump(arr)
        arr.map(&:attributes)
      end
    end
  end
end

Then you can transparently serialize and deserialize the education array in your User model:

class User
   # ...
   serialize :education, Education::ArraySerializer
   # ...
end

This solution should allow you to validate individual attributes of Education objects with built-in Rails validators, embed them in a nested form, and so on.

Important: I wrote the code above without testing it, so it might need a few modifications.