如何在Rails中显示列总和 [英] How to Show Sum of Column in Rails

问题描述

我想在我的模型Earning中显示列名称 money的总和。
在rails控制台中，我可以轻松获得所需的金额 Earning.sum（：money）并显示金额。

I want to display the sum of a column name "money" in my model Earning. In the rails console, I can easily get the sum I want Earning.sum(:money) and it shows the sum.

earnings_controller.rb

def index
  @earnings = Earning.sum(:money)
end

index.html.erb

<p id="notice"><%= notice %></p>

<h1>Earnings</h1>

<table>
  <thead>
    <tr>
      <th>Money</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @earnings.each do |earning| %>
      <tr>
        <td><%= earning.money %></td>
        <td><%= link_to 'Show', earning %></td>
        <td><%= link_to 'Edit', edit_earning_path(earning) %></td>
        <td><%= link_to 'Destroy', earning, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<%= link_to 'New Earning', new_earning_path %>

它不断抛出此错误

NoMethodError in Earnings#index

到目前为止我尝试过的事情

我很困惑。我尝试将索引操作更改为@earnings = income.sum（：money），这给了我这个错误 EarningsController＃index中的NameError。在此处，我也看到了类似的问题，但由于我认为问题在我的索引中。 html.erb，它并没有太大帮助。如前所述，该代码可在Rails控制台中使用。
预先感谢您的任何帮助。

I am stumped. I've tried changing the index action to @earnings = earnings.sum(:money) and that gave me this error "NameError in EarningsController#index". I also saw a similar problem here but since I think the issue is in my index.html.erb, it didn't help much. As I said earlier the code works in the Rails Console. Thank you in advance for any help.

推荐答案

因此，您在使用@earnings时并没有正确使用在您的视图中，您将收入用作对象的集合，但在控制器中@earnings被定义为金钱的总和，但您没有使用它，如果您确实需要此总和，则可以设置两个实例变量fiest @earnings = Earning.all第二个是@money_sum = Earnings.sum（：money），然后您可以在某处以= @money_sum的形式显示总和，然后可以通过@earnings进行迭代以在视图中创建一些链接。

So you are not using @earnings in a proper way, in your view you use earnings as a collecion of objects, but in controller @earnings are defined as a sum of money but you are not using it, if you really need this sum, you can set two instance variables fiest @earnings = Earning.all and the second one @money_sum = Earnings.sum(:money) and then you can display somewhere your sum as = @money_sum, then you can iterate by @earnings to create some linka in your view

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