til/rails/convert-json-field-to-hash-with-indifferent-access.md

Convert JSON Field To Hash With Indifferent Access

Let's say we have an Event model whose backing table includes a JSONB (or JSON) field called details.

When we access details in a Rails context, digging into that nested data we have to use string keys throughout. However, we may have existing related code that is dealing with this shape of data using symbol keys. This might put us in a position where we have to rework a bunch of existing code or do defensive coding like details[:user] || details["user"].

To avoid that, we can instead have the Event model override details converting that underlying data to HashWithIndifferentAccess before returning it.

class Event < ApplicationRecord
  def details
    data = super
    return data if data.nil?
    
    case data
    when Array
      data.map { |item| item.is_a?(Hash) ? item.with_indifferent_access : item }
    when Hash
      data.with_indifferent_access
    else
      data
    end
  end
end

With this in place, anywhere in the codebase where we access details on an instance of Event we will be able to use string or symbol keys interchangeably.