导轨的has_many：在与QUOT通过总和属性;子对象＆QUOT; - ＆GT; SQL Toughy [英] Rails has_many :through sum attribute on "child objects" --> SQL Toughy

问题描述

我有三个，一对许多的关系，一个的has_many：通过的关联和对象与属性我想总结。

I have three, one-to-many relationships, a has_many :through association and an object with an attribute I'd like to sum.

这听起来可能很傻，但假设例如棒球为主题的应用程序：

This may sound silly, but assume for example a baseball-themed app:

:league has_many :teams 
:team has_many :users   
:league has_many :homeruns, :through => :users
:user has_many :homeruns 

我想做的事情，在联赛中有什么显示页面列表中的每个小组在各自的联赛，总结有多少英尺在本垒打每个团队都有，累计。 （英尺是一个属性本垒打）

What I want to do, on the league show page is list each team in the respective league, and sum how many feet in homeruns each team has, cumulatively. (Feet is an attribute on homerun.)

最近我现在可以得到的是 @ league.homeruns.sum（：英尺）（显示多少在每个联盟本垒打总距离），但我想这样做在团队的水平，筛选的​​联赛。

The closest I can get now is @league.homeruns.sum(:feet) (showing how much total distance in homerun per league) but I want to do this at the team level, filtered by league.

有意义吗？任何帮助将是深深的AP preciated。

Make sense? Any help would be deeply appreciated.

推荐答案

如果您添加：团队的has_many：本垒打，通过：用户，然后你可以用 team.homeruns.sum（：英尺）来让你每队以后有什么，对不对？或许，这将是最好的移动到这一点的方法，你的小组型号：

If you add :team has_many :homeruns, through: :users, you could then use team.homeruns.sum(:feet) to get what you're after per team, right? It would probably be best to move this into a method in your team model:

# team.rb
has_many: homeruns, through: :users

def total_homerun_distance
  self.homeruns.sum(:feet)
end

要然后列出各队的特定联赛，只是通过各小组属于该<$迭代C $ C>联赛在视图中，包裹在任何你想要的HTML。例如，以显示它作为表

To then list all the teams for a particular league, just iterate through each team belonging to that league in the view, wrapped in whatever HTML you want. For example, to display it as a table:

# views/leagues/show.html.erb
<table>
<% @league.teams.each do |team| %>
  <tr>
    <td><%= team.name %></td>
    <td><%= team.total_homerun_distance %></td>
  </tr>
<% end %>
</table>

这篇关于导轨的has_many：在与QUOT通过总和属性;子对象＆QUOT; - ＆GT; SQL Toughy的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！