ruby-on-rails - 基于枚举值的自定义顺序

Question

我为角色定义了这个枚举:

enum role: {ordinary: 0, manager: 1, admin: 2}

我想按以下顺序订购一组对象:

admin (first all admins)
ordinary (then all ordinaries)
manager (and lastly all managers)

这可能吗？

Answer 1

对此的解决方案:

class YourModel < ActiveRecord::Base
  ROLE_ORDERS = [2, 0, 1]

  scope :order_by_role, -> {
    order_by = ['CASE']
    ROLE_ORDERS.each_with_index do |role, index|
      order_by << "WHEN role=#{role} THEN #{index}"
    end
    order_by << 'END'
    order(order_by.join(' '))
  }
end

那么您的查询将像这样简单:

YourModel.order_by_role

生成的查询是:

SELECT * from your_models
ORDER BY ( CASE
           WHEN role=2 THEN 0
           WHEN role=0 THEN 1
           WHEN role=1 then 2
           END
         )

来自 this 的良好引用