需要通过关系在 has_many 的连接模型上创建和更新属性

Question

我有以下型号：

class Individual < ActiveRecord::Base
  has_many visits
  has_many cities, :through => visits
  accepts_nested_attributes_for :visits, reject_if: proc { |a| a[:city_id].blank? }, allow_destroy: true
end

class Visit < ActiveRecord::Base
  belongs_to individual
  belongs_to city
end

class City < ActiveRecord::Base
  has_many visits
  has_many individuals, :through => visits
end

我正在尝试为每个人开发一个表格，列出我数据库中的所有城市，并允许他们勾选他们访问过的城市，然后添加有关该城市的一些基本属性。我目前拥有的是：

             <%= form_for(individual) do |f| %>
                  <% for city in cities.each do %>
                    <tr>
                      <td>
                          <%= check_box_tag "individual[visits_attributes][][city_id]", city_id.id, individual.cities.include?(city) %>
                      </td>
                      <td>
                        <label>How good was your visit here?</label>
                        <%= select_tag "individual[visits_attributes][][sentiment]", options_for_select([ ...... ])) %>
                      </td>
                      <td>
                        <label>What was the weather like?</label>
                        <%= select_tag "individual[visits_attributes][][weather]", options_for_select([ ...... ])) %>
                      </td>
                      <td>
                        <label>Where did you stay?</label>
                        <%= select_tag "individual[visits_attributes][][accomodation]", options_for_select([ ...... ])) %>
                      </td>
                    </tr>
                  <% end %>
                  <%= f.submit "Update", :class => "btn" %>
              <% end %>

这是一种工作方式，但它只是感觉不对劲而且不正常。此外，它会创建重复记录，我还不能让它删除记录。

任何人都可以提出更好的方法吗？或者帮我重构我已经拥有的东西？

Answer 1

这就是我最终解决它的方法。

结合@carlos 的输入，我使用 Ryan Bates 的助手动态添加新的nested_attributes 字段，但将其更改为在我的城市列表中工作

<%= form_for(individual) do |f| %>
  <% for city in cities.each do %>
    <% if individual.visits.include?(city) %>
      <% visit = f.object.visits.find_by_city_id(city.id) %>
      <%= f.fields_for(:visits, visit, child_index: visit.id ) do |existing_visit| %>
        <tr>
          <td>
              <%= check_box_tag "individual[visits_attributes][#{visit.id}][city_id]", city.id, individual.visits.include?(city) %>
              <%= existing_visit.hidden_field :_destroy %>
          </td>
          <td>
            <label>How good was your visit here?</label>
            <%= existing_visit.select :sentiment, options_for_select([ ...... ])) %>
          </td>
          <td>
            <label>What was the weather like?</label>
            <%= existing_visit.select :weather, options_for_select([ ...... ])) %>
          </td>
          <td>
            <label>Where did you stay?</label>
            <%= existing_visit.select :accomodation, options_for_select([ ...... ])) %>
          </td>
        </tr>
      <% end %>
    <% else %>
      <% visit = f.object.visits.build %>
      <% random_index = city.id.to_s+"_"+Time.now.to_i.to_s %>
      <%= f.fields_for(:visits, visit, child_index: random_index) do |new_visit| %>
        <tr>
          <td>
              <%= check_box_tag "individual[visits_attributes][#{random_index}][city_id]", city.id, nil %>
          </td>
          <td>
            <label>How good was your visit here?</label>
            <%= new_visit.select :sentiment, options_for_select([ ...... ])) %>
          </td>
          <td>
            <label>What was the weather like?</label>
            <%= new_visit.select :weather, options_for_select([ ...... ])) %>
          </td>
          <td>
            <label>Where did you stay?</label>
            <%= new_visit.select :accomodation, options_for_select([ ...... ])) %>
          </td>
        </tr>
      <% end %>
    <% end %>
    <%= f.submit "Update", :class => "btn" %>
  <% end %>
<% end %>

关键在于使用 if 语句检查记录是新记录还是现有记录，然后在 fields_for 帮助器上正确设置 child_index:。

我还必须使用 check_box_tag 而不是 .check_box 帮助器，这样它就不会产生隐藏的复选框字段。

当用户取消选中访问城市旁边的框时，我使用 Javascript 触发隐藏字段删除记录。

如果您需要更多详细信息，请与我们联系。

Answer 2

我没有时间写一个完整的答案，但要点是你想使用fields_for 来输出对象的关联字段。这在 Rails 中也称为“嵌套模型表单”。

查看这些资源以获得帮助：
Nested Model Form Railscast
Rails API fields_for