问题：
nil的未定义方法：关于视图和模型关系的NilClass
范文昌
我有一个非常基本的应用程序，由商店和属于商店的产品组成。我从产品表单中很好地提取了store ID，但每次尝试在产品视图中显示store中的属性时，都会出现未定义的方法错误。
products\u控制器。rb型
class ProductsController < ApplicationController
before_action :set_product, only: [:show, :edit, :update, :destroy]
# GET /products
# GET /products.json
def index
@products = Product.all
end
# GET /products/1
# GET /products/1.json
def show
end
# GET /products/new
def new
@product = Product.new
@stores = Store.all
end
# GET /products/1/edit
def edit
end
# POST /products
# POST /products.json
def create
@product = Product.new(product_params)
respond_to do |format|
if @product.save
format.html { redirect_to @product, notice: 'Product was successfully created.' }
format.json { render action: 'show', status: :created, location: @product }
else
format.html { render action: 'new' }
format.json { render json: @product.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /products/1
# PATCH/PUT /products/1.json
def update
respond_to do |format|
if @product.update(product_params)
format.html { redirect_to @product, notice: 'Product was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: @product.errors, status: :unprocessable_entity }
end
end
end
# DELETE /products/1
# DELETE /products/1.json
def destroy
@product.destroy
respond_to do |format|
format.html { redirect_to products_url }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_product
@product = Product.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def product_params
params.require(:product).permit(:name, :description, :imageurl, :url, :price, :Store_id, store_attributes: [:id, :name, :description])
end
end
product.rb
class Product < ActiveRecord::Base
belongs_to :store
has_many :pins
validates_presence_of :name, :url, :price
end
产品表单（_form.html.erb）
<%= form_for(@product) do |f| %>
<% if @product.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(@product.errors.count, "error") %> prohibited this product from being saved:</h2>
<ul>
<% @product.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="form-group">
<%= f.label :name, "Name" %>
<%= f.text_field :name, class: "form-control" %>
</div>
<div class="form-group">
<%= f.label :description, "Description" %>
<%= f.text_area :description, class: "form-control" %>
</div>
<div class="form-group">
<%= f.label :imageurl, "Image" %>
<%= f.text_field :imageurl, class: "form-control" %>
</div>
<div class="form-group">
<%= f.label :url, "Web Address" %>
<%= f.text_field :url, class: "form-control" %>
</div>
<div class="form-group">
<%= f.label :price, "Price" %>
$<%= f.text_field :price, class: "form-control" %>
</div>
<div class="form-group">
<%= collection_select(:product, :Store_id, Store.all, :id, :name, {:prompt=> "Select A Store"}, {:class => "form-control"} ) %>
</div>
<div class="form-group">
<%= f.submit class: "btn btn-primary" %>
</div>
<% end %>
<%= params.inspect %>
store.rb
class Store < ActiveRecord::Base
has_many :products
has_many :pins, through: :products
accepts_nested_attributes_for :products, :allow_destroy => true
end
以及有问题的产品视图（nil： NilClass的未定义方法“名称”）：
<p id="notice"><%= notice %></p>
<p>
<strong>Name:</strong>
<%= @product.name %>
</p>
<p>
<strong>Description:</strong>
<%= @product.description %>
</p>
<p>
<strong>Store Id:</strong>
<%= @product.Store_id %>
</p>
<p>
<strong>Store Name:</strong>
<%= @product.store.name %>
</p>
<p>
<strong>Image:</strong>
<%= @product.imageurl %>
</p>
<p>
<strong>Url:</strong>
<%= @product.url %>
</p>
<p>
<strong>Price:</strong>
$<%= @product.price %>
</p>
<%= params.inspect %>
<%= link_to 'Edit', edit_product_path(@product) %> |
<%= link_to 'Back', products_path %>
使用Rails控制台查找属于我引用的商店的所有产品，我最终得出以下结论：
Store.find(2).products
Store Load (0.2ms) SELECT "stores".* FROM "stores" WHERE "stores"."id" = ? LIMIT 1 [["id", 2]]
Product Load (0.4ms) SELECT "products".* FROM "products" WHERE "products"."store_id" = ? [[nil, 2]]
=> #<ActiveRecord::Associations::CollectionProxy [#<Product id: 4, name: "Test Product", description: "This is a test product", imageurl: "www.test.com/test.jpg", url: "www.test.com", price: #<BigDecimal:7fcd7ca620b0,'0.12E2',9(36)>, created_at: "2013-12-21 23:38:03", updated_at: "2013-12-21 23:38:03", Store_id: 2>, #<Product id: 5, name: "TEST", description: "TEST", imageurl: "", url: "www.ggooogle.com", price: #<BigDecimal:7fcd7ca61318,'0.12E2',9(36)>, created_at: "2013-12-24 01:27:10", updated_at: "2013-12-24 01:27:10", Store_id: 2>]>
2.0.0p247 :012 >
这是我在错误页面上的完整跟踪：
app/views/products/show.html.erb:20:in `_app_views_products_show_html_erb___2944853465650674919_70211283450300'
actionpack (4.0.1) lib/action_view/template.rb:143:in `block in render'
activesupport (4.0.1) lib/active_support/notifications.rb:161:in `instrument'
actionpack (4.0.1) lib/action_view/template.rb:141:in `render'
actionpack (4.0.1) lib/action_view/renderer/template_renderer.rb:49:in `block (2 levels) in render_template'
actionpack (4.0.1) lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
activesupport (4.0.1) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.1) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.1) lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
actionpack (4.0.1) lib/action_view/renderer/template_renderer.rb:48:in `block in render_template'
actionpack (4.0.1) lib/action_view/renderer/template_renderer.rb:56:in `render_with_layout'
actionpack (4.0.1) lib/action_view/renderer/template_renderer.rb:47:in `render_template'
actionpack (4.0.1) lib/action_view/renderer/template_renderer.rb:17:in `render'
actionpack (4.0.1) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionpack (4.0.1) lib/action_view/renderer/renderer.rb:23:in `render'
actionpack (4.0.1) lib/abstract_controller/rendering.rb:127:in `_render_template'
actionpack (4.0.1) lib/action_controller/metal/streaming.rb:219:in `_render_template'
actionpack (4.0.1) lib/abstract_controller/rendering.rb:120:in `render_to_body'
actionpack (4.0.1) lib/action_controller/metal/rendering.rb:33:in `render_to_body'
actionpack (4.0.1) lib/action_controller/metal/renderers.rb:26:in `render_to_body'
actionpack (4.0.1) lib/abstract_controller/rendering.rb:97:in `render'
actionpack (4.0.1) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
activesupport (4.0.1) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/usr/local/rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/benchmark.rb:296:in `realtime'
activesupport (4.0.1) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
activerecord (4.0.1) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:40:in `render'
actionpack (4.0.1) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (4.0.1) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (4.0.1) lib/abstract_controller/base.rb:189:in `process_action'
actionpack (4.0.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (4.0.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (4.0.1) lib/active_support/callbacks.rb:413:in `_run__50926827859438065__process_action__callbacks'
activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (4.0.1) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (4.0.1) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.1) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (4.0.1) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
activerecord (4.0.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (4.0.1) lib/abstract_controller/base.rb:136:in `process'
actionpack (4.0.1) lib/abstract_controller/rendering.rb:44:in `process'
actionpack (4.0.1) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.0.1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.0.1) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:680:in `call'
warden (1.2.3) lib/warden/manager.rb:35:in `block in call'
warden (1.2.3) lib/warden/manager.rb:34:in `catch'
warden (1.2.3) lib/warden/manager.rb:34:in `call'
rack (1.5.2) lib/rack/etag.rb:23:in `call'
rack (1.5.2) lib/rack/conditionalget.rb:25:in `call'
rack (1.5.2) lib/rack/head.rb:11:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/flash.rb:241:in `call'
rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/cookies.rb:486:in `call'
activerecord (4.0.1) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.1) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.1) lib/active_support/callbacks.rb:373:in `_run__448513151921752681__call__callbacks'
activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.1) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.1) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
railties (4.0.1) lib/rails/engine.rb:511:in `call'
railties (4.0.1) lib/rails/application.rb:97:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
/usr/local/rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
/usr/local/rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
/usr/local/rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'
Request
Parameters:
{"id"=>"6"}
共有1个答案
水渊
属于方法负责定义关联模型的方法。您已经说过产品属于：store，所以Rails定义了一个store方法，该方法假设您有一个store id属性。但是，您没有store\u id属性，您有store\u id属性。所以产品。store的计算结果为nil，您将得到所得到的错误。
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