Ruby on Rails，显示来自多个模型实例的多个属性

Question

In my Ruby on Rails project I have a Country model class and a Proposal model class. Each Country has many Proposals and each Proposal belongs to a Country. Each Proposal has 30 questions (attributes). In my view page, I want to display each question for every proposal that a country has.

So far, I have:

<div class="relative"> 
   <% @country.proposals.each do |proposal| %> 
     <h2>Food and Medicine:</h2><br>
         <div class="relative2">
           <p>List of prohibited drugs:</p>
           <p><% proposal.q1 %></p>
         </div>
     <h2>Liquids and Gels:</h2><br>
         <div class="relative2">
           <p>List of prohibited liquids/gels:</p>
           <p><% proposal.q2 %></p>
           ...
      ...
   <% end %>
</div>

The headings appear fine whenever the country has a proposal associated with it. However, the proposal attributes do not appear where I have placed them (in between the headings). I can confirm the attributes are not empty.

Proposal table:

create_table "proposals", force: :cascade do |t|
  t.string   "status",     default: "Pending"
  t.text     "q1"
  t.text     "q2"
  ...
  ...
  t.text     "q29"
  t.text     "q30"
  t.datetime "created_at",                     null: false
  t.datetime "updated_at",                     null: false
  t.integer  "country_id"
end

Answer 1

You forgot an equal sign. You should do:

<p><%= @proposals_q2 %></p>

Instead of:

<p><% @proposals_q2 %></p>

In addition you should remove the equal sign from your loop.

<% @country.proposals.each do |proposals| %>

Instead of:

<%= @country.proposals.each do |proposals| %>

In ERB, <%= expression %> is used to inject the evaluated expression into the DOM. <% expression %> is used to evaluate the expression and not do anything with it. You don't want the result of @country.proposals.each {...} to be evaluated on the first line and injected into the DOM, so you want it without the equal sign, while you do want each of the instance variables to be injected into the DOM, so you want them with the equal sign.

By the way, I assume that @proposals_q1 , @proposals_q2 , etc. are initialized in the controller action. If instead you have q1 , q2 , etc. as attributes on the Proposal model, then instead of using @proposals_q1 you should do something like:

<div class="relative"> 
   <% @country.proposals.each do |proposal| %> 
     <h2>Food and Medicine:</h2><br>
         <div class="relative2">
           <p>List of prohibited drugs:</p>
           <p><%= proposal.q1 %></p>
         </div>
     <h2>Liquids and Gels:</h2><br>
         <div class="relative2">
           <p>List of prohibited liquids/gels:</p>
           <p><%= proposal.q2 %></p>
           ...
      ...
   <% end %>
</div>

Answer 2

You're using <%= and <% backwards. <%= outputs stuff to the page. <% runs Ruby code but doesn't output anything.

As it stands, you are outputting the result of <%= @country.proposals.each , and you are not outputting the <% @proposals_q1 . That means that, inside the loop, the line <% @proposals_q1 %> has absolutely no effect, but after the entire loop is done, <%= @country.proposals.each... outputs proposals .

You need to use <%= @proposals_q1 %> to output the contents of that variable, inside the markup being written inside your loop, and you need to use <% @country.proposals.each... %> because there is no useful output generated by that use of <%= .

Answer 3

change this '

<% @proposals_q1 %>

" to this: "

<%= @proposals_q1 %>

"