ruby-on-rails - 在 Active Record 类中定义类方法

Question

模式中的设置表:

create_table "settings", :force => true do |t|
  t.string   "name"
  t.string   "value"
  t.datetime "created_at"
  t.datetime "updated_at"
end

设置表有这些记录:

{name: "notification_email", value: "hello@monkey.com"}
{name: "support_phone", value: "1234567"}

我希望 Setting.notification_email 函数返回“hello@monkey.com”，Setting.support_phone 函数返回“1234566”。

这是我的 setting.rb 中的内容:

class Setting < ActiveRecord::Base
  class << self
    all.each do |setting|
      define_method "#{setting.name}".to_sym do
        setting.value.to_s
      end 
    end 
  end 
end

但是当我在控制台输入 Setting.notification_email 时，它给了我一个错误:

NameError: undefined local variable or method `all' for #<Class:0x000000053b3df0>
    from /home/adam/Volumes/derby/app/models/setting.rb:7:in `singletonclass'
    from /home/adam/Volumes/derby/app/models/setting.rb:2:in `<class:Setting>'
    from /home/adam/Volumes/derby/app/models/setting.rb:1:in `<top (required)>'
    ...

Answer 1

使用 define_singleton_method - 即

class Setting < ActiveRecord::Base

  self.all.each do |instance|
    define_singleton_method(instance.name) do
      instance.value.to_s
    end
  end
end