# File activerecord/lib/active_record/readonly_attributes.rb, line 25
def attr_readonly(*attributes)
  self._attr_readonly = Set.new(attributes.map(&:to_s)) + (_attr_readonly || [])
end

Attributes listed as readonly will be used to create a new record but update operations will ignore these fields.

You can assign a new value to a readonly attribute, but it will be ignored when the record is updated.

Examples

class Post < ActiveRecord::Base
  attr_readonly :title
end

post = Post.create!(title: "Introducing Ruby on Rails!")
post.update(title: "a different title") # change to title will be ignored

# File activerecord/lib/active_record/readonly_attributes.rb, line 30
def readonly_attributes
  _attr_readonly
end

Returns an array of all the attributes that have been specified as readonly.