ruby-on-rails - Rails 3 中的嵌套属性

Question

任何人都可以带我了解 Rails 3 中的嵌套属性吗？

我有两个模型:证书和托管人，相关如下:

证书型号:

class Certificate < ActiveRecord::Base
  belongs_to :shareholder
  belongs_to :custodian
  belongs_to :issuer

  accepts_nested_attributes_for :custodian, :shareholder, :issuer 
end

证书 Controller :

class CertificateController < ApplicationController
  def issue
    @certificate = Certificate.new
    @certificate.custodian.build
  end
end

我的看法:

<% form_for(:certificate, :url => {:action => 'testing'}) do |f| -%>

<div id="error">
    <%= f.error_messages %>
</div>

  <%= f.label :number, "Certificate Number" %>
  <%= f.text_field :number %>   <br/>

    <%= f.label :num_of_shares, "Number Of Shares" %>
    <%= f.text_field :num_of_shares %> <br/>

    <% f.fields_for :custodian do |custodian| -%>
        <%= custodian.label :name, "Custodian Name" %>
        <%= custodian.text_field :name %>
    <% end -%>

    <%= f.submit "Issue Certificate", :disable_with => 'Working....' %>

<% end -%>

现在，出于某种原因，在我的 Controller 第 4 行: @certificate.custodian.build

我收到此错误: undefined method 'build' for nil:NilClass
任何人都可以帮忙吗？

Answer 1

使用belongs_to，它应该是

@certificate.build_custodian