Question

我试图通过指向Module常量来设置属性的默认值，但事情不会计划。相关代码包括：

[lib/establishments.rb]
module Establishments
  BAR = "Bar"
  RESTAURANT = "Restaurant"
  BENEFIT = "Benefit"
end

[20140321164012_add_type_to_discount]
include Establishments
class AddTypeToDiscount < ActiveRecord::Migration

  def change
    add_column :discounts, :type, :string, :default => Establishments::RESTAURANT
  end
end

rake db:migrate

以上代码导致：

rake aborted!
An error has occurred, this and all later migrations canceled:

uninitialized constant Establishments/home/bob/Dev/app/db/migrate/20140321164012_add_type_to_discount.rb:1:in `<top (required)>'

在我看来，/lib未找到rake路径。我不确定如何影响它。

我也尝试过添加：

require 'lib/establishments.rb'

在迁移文件的顶部，但是抱怨没有这样的文件。

Answer 1

尝试：

require "#{Rails.root}/lib/establishments"

然后您就可以使用Establishments::RESTAURANT

了

Answer 2

使用require_relative '../../lib/establishments'代替include Establishments

Answer 3

感谢您的回答，一切都是有效的 - 正如我发现的那样（同样有效）

require File.expand_path('lib/establishments')

将模块常量引用为：ActiveRecord :: Migration中的默认值时出错

3 个答案: