使用动态嵌套表单在编辑页面中添加新字段

Question

我正在尝试创建一个具有动态添加和删除嵌套模型字段的表单。我已经非常关注 ryanb 的 railcast (http://railscasts.com/episodes/197-nested-model-form-part-2) 做了一些小改动以使其与 Rails 4.0 兼容

唯一不起作用的是在编辑页面上添加新字段。现在，如果我添加一个新字段，它将采用以前存在的字段的结构和数据。

例如，假设我创建了一个问题“FooBarBaz”，答案是“foo”和“bar”。我意识到我缺少“baz”，所以我进入编辑问题，当我单击新字段时，页面现在显示答案“foo”、“bar”、“foo”、“bar”。相反，我想要“foo”、“bar”和一个空字段。

routes.rb

resource :questions do
  resource :answers
end

问题.rb

has_many :answers, dependent: :destroy
accepts_nested_attributes_for :answers, allow_destroy: true

answer.rb

belongs_to :question

_form.html.erb

<%= simple_form_for @question do |f| %>
  <div class="question">
    <%= f.input :name %>
    <div class="answer">
      <%= f.simple_fields_for :answers do |g| %>
        <%= render "answer_fields", f: g %>
      <% end %>
      <p><%= link_to_add_fields("Add Question", f, :answers) %></p>
    </div>
  </div>
<% end %>

application_helper.rb

def link_to_add_fields(name, f, association)
  new_object = f.object.class.reflect_on_association(association).klass.new
  fields = f.simple_fields_for association, child_index: "new_#{association}" do |builder|
    render(association.to_s.singularize + "_fields", :f => builder)
  end
  link_to_function(name, "add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")")
end

questions.js

function add_fields(link, association, content) {
  var new_id = new Date().getTime();
  var regexp = new RegExp("new_" + association, "g")
  $(link).parent().before(content.replace(regexp, new_id));
}

Answer 1

意识到这是 application_helper.rb 的问题。更具体地说，应该是，

fields = f.simple_fields_for association, new_object, child_index: "new_#{association}" do |builder|
  render(association.to_s.singularize + "_fields", :f => builder)
end

new_object 丢失的地方。