ruby-on-rails - 初始化虚拟属性

Question

我有一个 IncomingEmail带 attachments 的模型虚拟属性:

class IncomingEmail < ActiveRecord::Base  
  attr_accessor :attachments
end

我想要 attachments要初始化为 [] 的虚拟属性而不是 nil这样我就可以:

>> i = IncomingEmail.new
=> #<IncomingEmail id: nil,...)
>> i.attachments << "whatever"

无需首次设置 i.attachments至 [] (换句话说，我希望这个虚拟属性默认为空数组而不是 nil )

Answer 1

使用 after_initialize打回来

class IncomingEmail < ActiveRecord::Base  
  attr_accessor :attachments
  def after_initialize
    self.attachments ||= [] # just in case the :attachments were passed to .new
  end
end