RailsによるアジャイルWebアプリケーション開発

第9章 タスクD：カートの作成

before_destroyとbutton_toの使い方に注意。

• app/models/product.rb

class Product < ActiveRecord::Base
  validates :title, :description, :image_url, presence: true
  validates :price, numericality: { greater_than_or_equal_to: 0.01 }
  validates :title, uniqueness: true
  validates :image_url, allow_blank: true, format: {
    with: %r{\.(gif|jpg|png)\z}i,
    message: 'はGIF、JPG、PNG画像のURLでなければなりません'
  }

  has_many :list_items

  before_destroy :ensure_not_referenced_by_any_line_item

  private

  def ensure_not_referenced_by_any_line_item
    return true if line_items.empty?
    errors.add(:base, '品目が存在します')
    false
  end
end

• app/views/store/index.html.haml

- if notice
  %p#notice= notice

%h1 Pragmaticカタログ

- @products.each do |product|
  .entry
    = image_tag(product.image_url)
    %h3= product.title
    = sanitize product.description
    .price_line
      %span.price= number_to_currency product.price
      = button_to 'カートに入れる', line_items_path(product_id: product)

• spec/controllers/line_items_spec.rb

require 'rails_helper'

RSpec.describe LineItemsController, type: :controller do
  describe 'POST create' do
    let(:product) { create(:product) }

    it 'LineItem が登録されること' do
      expect {
        post :create, product_id: product
      }.to change(LineItem, :count).by(1)
    end

    it 'redirects to carts#show' do
      post :create, product_id: product
      expect(response).to redirect_to cart_path(assigns(:line_item).cart)
    end
  end
end