key_mapping.rb

module KeyMapping
  def self.included(base)
    base.instance_variable_set(:@key_mappings, {})
    base.extend(ClassMethods)
    base.send(:include, InstanceMethods)
  end

  module ClassMethods
    attr_reader :key_mappings

    def inherited(klass)
      super
      klass.instance_variable_set(:@key_mappings, key_mappings.dup)
    end

    def key(props)
      path, name = props.to_a.first
      name = path if name.nil?
      key_mappings[name] = path.split('.').map do |value|
        value.match(/^(\d+)$/) ? $1.to_i : value.to_sym
      end
    end
  end

  module InstanceMethods
    def initialize(hash = {})
      self.class.key_mappings.each do |key, path|
        self[key] = hash.dig(*path)
      end
    end
  end
end

class Resource < Hash
  include KeyMapping
end

class Video < Resource
  key 'details.id' => :id
end

z = Video.new details: { id: 'blah' }

puts z[:id]