从另一个表中提取数据。

<% @checkouts.reverse.each do |checkout| %>
  <tr>
    <td><%= checkout.radio_num %></td>
    <th colspan="3"></th>
    <td><%= checkout.badge %></td>
    <th colspan="3"></th>
  </tr>
    <% @staffs.each do |staff| %>
        <% if checkout.badge == staff.badge %>
        <tr>
            <td><%= staff.name %></td>
            <th colspan="3"></th>
            <td><%= staff.dept %></td>
        </tr>
        <% end %>
    <% end %>   
  <tr>
    <td><%= link_to 'Edit', edit_checkout_path(checkout) %></td>
    <td><%= link_to 'Destroy', checkout, method: :delete, data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>

I'm new to ruby on rails, and I'm trying to create a checkout/return application for radios. Is there something I need to do within my views/checkouts to allow access to my Staffs table?

我是ruby on rails的新手，我正在尝试创建一个用于收音机的结账/返回应用程序。在我的视图/结帐过程中是否需要做一些事情来允许访问我的员工表?

I get the error on line 8

我在第8行得到了错误。

undefined method `badge' for nil:NilClass

无定义方法“徽章”为nil:NilClass。

This is the controller code that was asked

这是被问到的控制器代码。

class StaffsController < ApplicationController

def index
@staffs = Staff.all
end

def show
@staff = Staff.find(params[:id])
end

def new
@staff = Staff.new
end

def create
@staff = Staff.new(staff_params)
if @staff.save
  redirect_to(:action => 'index')
else
  render('new')
end
end

def edit
@staff = Staff.find(params[:id])
end

def update
@staff = Staff.find(params[:id])
if @staff.update_attributes(staff_params)
  redirect_to(:action => 'show', :id => @staff.id)
else
  render('index')
end
end

def delete
@staff = Staff.find(params[:id])
end

def destroy
Staff.find(params[:id]).destroy
redirect_to(:action => 'index')
end

private

def staff_params
params.require(:staff).permit(:badge, :name, :dept)
end

end

Thanks!

谢谢!

2 个解决方案

#1

The view in question is the checkout/index view which will reference the CheckoutController's index action/method. This is due to rails convention over configuration. If the @staffs instance variable isn't defined on that controller method/action then a nil:NilClass error will be thrown.

问题的视图是签出/索引视图，它将引用CheckoutController的索引操作/方法。这是由于rails约定优于配置。如果在控制器方法/操作上没有定义@staff实例变量，则会抛出nil:NilClass错误。

Your controller should look something like this.

控制器应该是这样的。

class CheckoutController < ApplicationController
  def index
    # avoid calling ActiveRecord query methods in the view
    # Checkout.all.reverse or
    @checkouts = Checkout.order(created_at: :desc)
    @staffs = Staff.all
  end
end

It is also good practice to avoid logic in the views. It feels natural as a beginner to place logic in the view, but as time passes you will see your views become more complex and cognitive overhead increases.

在视图中避免逻辑也是很好的做法。作为一个初学者，在视图中放置逻辑是很自然的，但是随着时间的推移，你会看到你的观点变得更加复杂，认知开销也会增加。

Helper methods are a good place to start encapsulates some of logic in the view.

Helper方法是一个很好的起点，可以在视图中封装一些逻辑。

module CheckoutHelper
  def equal_badge?(checkout_badge, staff_badge)
    checkout_badge == staff_badge
  end
end

And call it in the view using

在视图中调用它。

<% if equal_badge(checkout.badge, staff.badge) %>

Another cool trick in rails is rendering partials for collections (what you have stored within the staff and checkout instance variables at the moment).

rails中的另一个很酷的技巧是为集合呈现部分(此时您已经将其存储在staff和checkout实例变量中)。

Create a _staff_list.html.erb which contains

创建一个_staff_list.html。erb包含

  <% if equal_badge(checkout.badge, staff.badge) %>
    <tr>
      <td><% staff.name %>
      <!-- etc, etc -->
  <% end %>

And in the checkouts/index view render that partial by

在checkouts/index视图中，呈现出部分by。

<%= render partial: "checkouts/staff_list", collection: @staffs, locals: { checkout: checkout } %>

It's more than you asked for, but I hope this helps a bit.

这比你要求的要多，但我希望这能有所帮助。

#2

you are using @checkout (on line 9) but the local variable you declare (on line 1) is actually called checkout

您使用的是@checkout(在第9行)，但是您声明的本地变量(在第1行)实际上称为checkout。

Likewise, you are using @staff but the variable you actually have available to you is staff

同样，您使用的是@staff，但是您实际上可以使用的变量是staff。

So for line 9 you should instead have:

所以对于第9行，你应该:

   <% if checkout.badge == staff.badge %>

Be aware that you do not need to use @variables inside your template unless they are something that was set up in the controller.

请注意，您不需要在模板中使用@variables，除非它们是在控制器中设置的。

In this case, it looks like you set up the variables: @staffs and @checkouts in the controller... they appear to be arrays of things. @staff and @checkout were not set up in the controller - they are just local variables, and so are correctly named without the@`

在本例中，它看起来像设置了变量:控制器中的@staff和@checkouts…它们看起来是一系列的东西。@staff和@checkout并不是在控制器中设置的——它们只是局部变量，所以正确地命名为“没有@”

#1