问我怎样才能在ActiveRecord中设置默认值？

class Item < ActiveRecord::Base  

  def initialize_with_defaults(attrs = nil, &block)

    initialize_without_defaults(attrs) do

      setter = lambda { |key, value| self.send("#{key.to_s}=", value) unless

        !attrs.nil? && attrs.keys.map(&:to_s).include?(key.to_s) }

      setter.call('scheduler_type', 'hotseat')

      yield self if block_given?

    end

  end

  alias_method_chain :initialize, :defaults

end

I have seen the following examples googling around:

  def initialize 

    supe

    self.status = ACTIVE unless self.status

  end

and

  def after_initialize 

    return unless new_record?

    self.status = ACTIVE

  end