Rails 4 未初始化的常量 Admin::Category

Question

我已经为我的所有默认模型生成了管理命名空间控制器，如下所示：

rails g scaffold_controller admin/categories name:string slug:string description:string icon_xlarge:string icon_large:string icon_medium:string icon_small:string status:integer

这会生成以下文件：

Harshas-MacBook-Pro:nomad harshamv$ rails g scaffold_controller admin/categories name:string slug:string description:string icon_xlarge:string icon_large:string icon_medium:string icon_small:string status:integer
Plural version of the model detected, using singularized version. Override with --force-plural.
      create  app/controllers/admin/categories_controller.rb
      invoke  erb
      create    app/views/admin/categories
      create    app/views/admin/categories/index.html.erb
      create    app/views/admin/categories/edit.html.erb
      create    app/views/admin/categories/show.html.erb
      create    app/views/admin/categories/new.html.erb
      create    app/views/admin/categories/_form.html.erb
      invoke  test_unit
      create    test/controllers/admin/categories_controller_test.rb

app/model/category.rb

class Category < ActiveRecord::Base

  extend FriendlyId

  friendly_id :name, use: :slugged

  has_and_belongs_to_many :venues

end

app/controller/admin/categories_controller.rb

class Admin::CategoriesController < ApplicationController
  before_action :set_admin_category, only: [:show, :edit, :update, :destroy]

  # GET /admin/categories
  def index
    @admin_categories = Admin::Category.all
  end

  # GET /admin/categories/1
  def show
  end

  # GET /admin/categories/new
  def new
    @admin_category = Admin::Category.new
  end

  # GET /admin/categories/1/edit
  def edit
  end

  # POST /admin/categories
  def create
    @admin_category = Admin::Category.new(admin_category_params)

    if @admin_category.save
      redirect_to @admin_category, notice: 'Category was successfully created.'
    else
      render :new
    end
  end

  # PATCH/PUT /admin/categories/1
  def update
    if @admin_category.update(admin_category_params)
      redirect_to @admin_category, notice: 'Category was successfully updated.'
    else
      render :edit
    end
  end

  # DELETE /admin/categories/1
  def destroy
    @admin_category.destroy
    redirect_to admin_categories_url, notice: 'Category was successfully destroyed.'
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_admin_category
      @admin_category = Admin::Category.find(params[:id])
    end

    # Only allow a trusted parameter "white list" through.
    def admin_category_params
      params.require(:admin_category).permit(:name, :slug, :description, :icon_xlarge, :icon_large, :icon_medium, :icon_small, :status)
    end
end

app/view/admin/categories/index.html.erb

<h1>Listing admin_categories</h1>

<table>
  <thead>
    <tr>
      <th>Name</th>
      <th>Slug</th>
      <th>Description</th>
      <th>Icon xlarge</th>
      <th>Icon large</th>
      <th>Icon medium</th>
      <th>Icon small</th>
      <th>Status</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @admin_categories.each do |admin_category| %>
      <tr>
        <td><%= admin_category.name %></td>
        <td><%= admin_category.slug %></td>
        <td><%= admin_category.description %></td>
        <td><%= admin_category.icon_xlarge %></td>
        <td><%= admin_category.icon_large %></td>
        <td><%= admin_category.icon_medium %></td>
        <td><%= admin_category.icon_small %></td>
        <td><%= admin_category.status %></td>
        <td><%= link_to 'Show', admin_category %></td>
        <td><%= link_to 'Edit', edit_admin_category_path(admin_category) %></td>
        <td><%= link_to 'Destroy', admin_category, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<%= link_to 'New Category', new_admin_category_path %>

我的尝试

我将控制器编辑如下

 # GET /admin/categories
  def index
    @admin_categories = Category.all
  end

  # GET /admin/categories/1
  def show
  end

  # GET /admin/categories/new
  def new
    @admin_category = Category.new
  end

  # GET /admin/categories/1/edit
  def edit
  end

  # POST /admin/categories
  def create
    @admin_category = Category.new(admin_category_params)

    if @admin_category.save
      redirect_to @admin_category, notice: 'Category was successfully created.'
    else
      render :new
    end
  end

当我转到localhost/admin/categories 并单击“新类别”时，我现在收到以下错误：

我的路线文件：

Rails.application.routes.draw do

  # Admin Routing
  namespace :admin do
    resources :categories, :cities, :countries, :lists, :oauths, :regions, :tags, :users, :user_groups, :venues, :venue_photos, :venue_reviews
  end

end

Answer 1

您在 routes.rb 的 namespace :admin 下定义了 resources :categories，所以您的 @ 中的这一行987654326@

<%= form_for(@admin_category) do |f| %>

应该是

<%= form_for([:admin, @admin_category]) do |f| %>

欲了解更多信息，请参阅此API

更新

第二个错误是因为这一行

params.require(:admin_category).permit(:name, :slug, :description, :icon_xlarge, :icon_large, :icon_medium, :icon_small, :status)

应该是

params.require(:category).permit(:name, :slug, :description, :icon_xlarge, :icon_large, :icon_medium, :icon_small, :status)

Answer 2

要访问命名空间之外的模型，您需要调用 ::Category.new 而不是 Admin::Category.new

Answer 3

正如您的错误所示，这是您调用表单的方式的问题。您的表单需要引用 admin 命名空间，如下所示：

<%= form_for [:admin, @category] do |f| %>

但是，脚手架构建文档的方式与我推荐的方式有很多不同。

我还建议简化脚手架控制器中的代码以引用简单的@category 和@categories，而不是@admin_category 和@admin_categories。

此外，模型不应位于 admin 命名空间中，因此 Admin::Category.new 应为 Category.new。其余的模型调用也应相应调整。