gistfile1.rb

class Foo < ActiveRecord::Base
  default_value_for :store, {}
  
  def entry_1= value
    store[:entry_1] = value
  end
end

Foo.new :entry_1 => 'bar'
# =>
# NoMethodError: You have a nil object when you didn't expect it!
# You might have expected an instance of Array.
# The error occurred while evaluating nil.[]