Rails 3 中的嵌套属性 [英] Nested Attributes in Rails 3

问题描述

谁能帮我介绍一下 Rails 3 中的嵌套属性?

我有两个模型:证书和托管人，相关如下:

证书模型:

班级证书

证书控制器:

class CertificateController <应用控制器定义问题@certificate = [e-mail]结尾结尾

我的观点:

<% form_for(:certificate, :url => {:action => 'testing'}) do |f|-％＞<div id="错误"><%= f.error_messages %>

<%= f.label :number, "证书编号" %><%= f.text_field :number %><br/><%= f.label :num_of_shares, "共享数量" %><%= f.text_field :num_of_shares %><br/><% f.fields_for :custodian do |custodian|-％＞<%= custodian.label :name, "保管人姓名" %><%= custodian.text_field :name %><%结束-%><%= f.submit "颁发证书", :disable_with =>'工作....' %><%结束-%>

现在，出于某种原因，在我的控制器第 4 行:@certificate.custodian.build

我收到此错误:undefined method 'build' for nil:NilClass

有人可以帮忙吗?

解决方案

accepts_nested_attributes_for 应该站在一对多关系的一方.

class Custodian <ActiveRecord::Basehas_many : 证书accepts_nested_attributes_for :certificates结尾

因此，在您看来，应该没有 fields_for :custodian，这是错误的一面.如果您必须从该视图构建证书，则必须列出可用的托管人，可能在选择框中.

can anyone please walk me through Nested Attributes in Rails 3?

I have two Models: Certificates and Custodians, related as follows:

Certificate Model:

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

  accepts_nested_attributes_for :custodian, :shareholder, :issuer 
end

Certificate Controller:

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

My View:

<% 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 -%>

Now, for some reason, in my controller on line 4: @certificate.custodian.build

I'm getting this error: undefined method 'build' for nil:NilClass

Can any one please help?

解决方案

accepts_nested_attributes_for should go on the side of one in the one-to-many relationship.

class Custodian < ActiveRecord::Base
  has_many :certificates
  accepts_nested_attributes_for :certificates
end

So, in your view, there should be no fields_for :custodian, it's on the wrong side. If you have to build a certificate from that view, you have to list custodians available, probably in a select box.

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