In Rails, how do I limit which attributes can be updated, without preventing them from being created?

Question

I have a situation where an attribute can be created through a JSON API. But once it is created, I want to prevent it from ever being updated.

This constraint causes my

Answer 1

There is not a nice way to do that as far as I know, you have to write a custom filter

before_update :prevent_attributes_update

def prevent_attribute_updates
  %w(attr1, attr2).each do |a|
    send("#{attr1}=", send("#{attr1}_was")) unless self.send("#{attr1}_was").blank?
  end
end