參考https://blog.skcript.com/implementing-categories-in-ruby-on-rails-14c2b5e77b34#.ugsdz8w8b
參考http://taomengdi99.logdown.com/posts/1420713

近日做了一個(gè)商品購物網(wǎng)站（https://github.com/AnattaGuo/jdstore2），想給admin賬戶添加商品分類功能。

1. 在命令端輸入rails g scaffold category name:string desc:text
   

   Snip20170305_20.png

2. 在命令端輸入rake db:migrate

3. 在命令端輸入rails generate migration AddColumnsToProducts category_id，然后輸入rake db:migrate
   

   Snip20170305_22.png

4. 建立product model和category model的relationship. 修改如下兩個(gè)文件：

#app/models/product.rb
belongs_to :category

Snip20170305_25.png

#app/models/category.rb
has_many :products

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#app/controllers/admin/products_controller.rb

class Admin::ProductsController < ApplicationController

  layout "admin"
  before_action :authenticate_user!
  before_action :admin_required

  def index
    if params[:category].blank?
      @products = Product.all
    else
      @category_id = Category.find_by(name: params[:category]).id
      @products = Product.where(:category_id => @category_id)
    end
  end

  def new
    @product = Product.new
    @categories = Category.all.map{|c| [ c.name, c.id ] }
  end

  def edit
    @product = Product.find(params[:id])
    @categories = Category.all.map{|c| [ c.name, c.id ] }
  end

  def update
    @product = Product.find(params[:id])
    @product.category_id = params[:category_id]

    if @product.update(product_params)
      redirect_to admin_products_path
    else
      render :edit
    end
  end

  def create
    @product = Product.new(product_params)
    @product.category_id = params[:category_id]

    if @product.save
      redirect_to admin_products_path
    else
      render :new
    end
  end

  private

  def product_params
    params.require(:product).permit(:title, :description, :quantity, :price, :image, :category_id)
  end
end

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 <%= select_tag(:category_id, options_for_select(@categories), :prompt => 'Select one!') %>

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new category.gif

這樣在http://localhost:3000/admin/products 下面就可看到catetory了

Snip20170305_38.png

最終分類成果演示：

new category-new product.gif