How to verify if an embedded field changed on before_save? - ruby

Question

I am running Ruby 2.1 and Mongoid 5.0 (no Rails).
I want to track on a before_save callback whether or not an embedded field has changed.
I can use the document.attribute_changed? or document.changed methods to check normal fields, but somehow these don't work on relations (embed_one, has_one, etc).
Is there a way of detecting these changes before saving the document?
My model is something like this
class Company
include Mongoid::Document
include Mongoid::Attributes::Dynamic
field :name, type: String
#...
embeds_one :address, class_name: 'Address', inverse_of: :address
#...
before_save :activate_flags
def activate_flags
if self.changes.include? 'address'
#self.changes never includes "address"
end
if self.address_changed?
#This throws an exception
end
end
One example of how I save my document is:
#...
company.address = AddressUtilities.parse address
company.save
#After this, the callback is triggered, but self.changes is empty...
#...
I have read the documentation and Google the hell out of it, but I can't find a solution?
I have found this gem, but it's old and doesn't work with the newer versions of Mongoid. I want to check if there is another way of doing it before considering on trying to fix/pull request the gem...

Answer 1

Adding these two methods to your Model and calling get_embedded_document_changes should provide you an hash with the changes to all its embedded documents:
def get_embedded_document_changes
data = {}
relations.each do |name, relation|
next unless [:embeds_one, :embeds_many].include? relation.macro.to_sym
# only if changes are present
child = 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
[ source: https://gist.github.com/derickbailey/1049304 ]