Private/protected accessors to attributes in Rails 4

Question

Supose that I have the following class:

class Foo < ActiveRecord::Base
    belongs_to :bar
end

In rails console I can do this:

foo = Foo.new
foo.bar_id = 3

But this can violates the encapsulation principle. I think that is better idea do:

foo = Foo.new
foo.bar = Bar.find(3);

And bar_id should be private/protected. This has nothing to do with the mass assignment and strong parameters but it is an security issue too.

Is there any way to set to private some attributes?

Answer 1

Is there a way to make Rails ActiveRecord attributes private?

class MyModel < ActiveRecord::Base

  private

  def my_private_attribute
    self[:my_private_attribute]
  end

  def my_private_attribute=(val)
    write_attribute :my_private_attribute, val
  end
end

Answer 2

I don't think just making the write accessor private or protected will reliably prevent change via update_attribute or mass assignment.

While it's not actually "private" per se, but you could get the desired effect by setting the attribute read_only, eg

attr_readonly :bar_id

and if you do need to update the value "private-ly," access it as @bar_id. Per the docs, "Attributes listed as readonly will be used to create a new record but update operations will ignore these fields."