Track dirty for not-persisted attribute in an ActiveRecord object in rails

Question

I have an object that inherits from ActiveRecord, yet it has an attribute that is not persisted in the DB, like:

 class Foo < ActiveRecord::Base
   attr_acces         


        

Answer 1

I'm using the attribute_will_change! method and things seem to be working fine.

It's a private method defined in active_model/dirty.rb, but ActiveRecord mixes it in all models.

This is what I ended up implementing in my model class:

def bar
  @bar ||= init_bar
end
def bar=(value)
  attribute_will_change!('bar') if bar != value
  @bar = value
end
def bar_changed?
  changed.include?('bar')
end

The init_bar method is just used to initialise the attribute. You may or may not need it.

I didn't need to specify any other method (such as define_attribute_methods) or include any modules. You do have to reimplement some of the methods yourself, but at least the behaviour will be mostly consistent with ActiveModel.

I admit I haven't tested it thoroughly yet, but so far I've encountered no issues.