get changes to mongoid document, including embedded documents

mongoid_document_changes_with_embedded.rb

module Mongoid
  module Document
    def changes_with_embedded
      field_data = get_previous_changes_for_model(self)
      embedded_data = get_embedded_document_changes(self)

      unless embedded_data.empty?
        field_data.merge embedded_data 
      end
    end

    private

    def get_embedded_document_changes(model)
      data = {}

      model.relations.each do |name, relation|
        next unless [:embeds_one, :embeds_many].include? relation.macro.to_sym

        # only if changes are present
        child = model.send(name.to_sym)
        next unless child
        next if child.previous_changes.empty?

        child_data = get_previous_changes_for_model(child)
        data[name] = child_data
      end

      data
    end

    def get_previous_changes_for_model(model)
      data = {}
      model.previous_changes.each do |key, change|
        data[key] = {:from => change[0], :to => change[1]}
      end
      data
    end
  end
end

当 relation 是 embeds_many 时，child 会是一个数组对象，Line 23 会报错