今天接著昨天的實作

7. 簡單建一個結帳功能

先建立一個 Order model:

$ rails g model Order total_amount:decimal coupon_code:string

在 db/migrate 目錄中找到新建立的 Migration:

class CreateOrders < ActiveRecord::Migration[6.1]
  def change
    create_table :orders do |t|
      t.decimal :total_amount, precision: 8, scale: 2
      t.string :coupon_code

      t.timestamps
    end
  end
end

別忘了執行:

$ rails db:migrate

order 也需要一個 controller:

$ rails g controller orders

# OrdersController
class OrdersController < ApplicationController
  def new
    @order = Order.new
  end

  def create
    @order = Order.new(order_params)
    if @order.save
      # Apply the coupon discount if a valid coupon code is provided
      if params[:coupon_code].present?
        books_coupon = BooksCoupon.find_by(code: params[:coupon_code])
        if books_coupon&.available?
          @order.total_amount = books_coupon.apply_discount(@order.total_amount)
          books_coupon.increment!(:used_count)
        else
          flash[:alert] = 'Invalid or expired coupon code.'
          render :new
          return
        end
      end

      @order.save
      redirect_to root_path, notice: 'Order placed successfully.'
    else
      render :new
    end
  end

  private

  def order_params
    params.require(:order).permit(:total_amount, :coupon_code)
  end
end        

8. 建立訂單的 view

<%= form_with(model: @order, url: orders_path) do |form| %>
  <div class="field">
    <%= form.label :total_amount %>
    <%= form.number_field :total_amount %>
  </div>

  <div class="field">
    <%= form.label :coupon_code %>
    <%= form.text_field :coupon_code %>
  </div>

  <div class="actions">
    <%= form.submit 'Place Order' %>
  </div>
<% end %>

9. 補上 orders 的 route

Rails.application.routes.draw do

  resources :books_coupons, only: [:new, :create, :index]
  resources :orders, only: [:new, :create]
  root 'orders#new'
end

這樣一來一個小小的折價券功能就經由 rails 的 CRUD 建立起來，總之想把 ruby on rails 學好的不二法門就是練熟 CRUD

預告

明天預計來介紹資料驗證，我們明天見！