带条件的订单元素

Question

我想用 2 个变量 (notifications(integer) & priority(integer[1, 2, 3])) 对我的组进行排序。

这就是我想要达到的顺序：

1.Group with notifications 
  a.Group with priority(1)
  b.Group with priority(2)
2. Group without notifications 
  a.Group with priority(1)
  b.Group with priority(2)
  c.Group with priority(3)

您认为最好的方法是什么？

Answer 1

首先，您必须以不同方式拆分订单。对我来说，订购群组的最简单方法是这样的：

1. Group notified without priority(3) 
2. Group not notified without priority(3) # We also add without priority in this step to avoid duplication
3. Group With the less priority

之后，您构建一些范围，并默认排序：

class Group < ApplicationRecord
  default_scope {order(priority: asc)} 

  scope :notified, -> { where.not(notifications: 0, priority: 3) }
  scope :not_notified, -> { where(notifications: 0).where.not(priority: 3) }
  scope :not_important, -> { where(priority: 3) }

end

最后，您像这样呈现您的组：

<% @groups = Group.all %>

<% @groups.notified.each do |group| %>
  Group notified 
<% end %>

<% @groups.not_notified.each do |group| %>
  Group not notified 
<% end %>

<% @groups.not_important.each do |group| %>
  Group not important 
<% end %>

带条件的订单元素

Order element with condition

ruby-on-rails

sql-order-by