Candy Shop

components.candy-item.js

import Component from '@ember/component';
import { computed } from '@ember/object';

export default Component.extend({
  tagName: 'li',

  classNames: ['candy-item'],

  isDiscountAllowed: computed.and('discount.{couponNotUsed,percent}', 'isOnSale'),

  discountedPrice: computed('discount.percent', function() {
    const price = this.get('price');
    const discountPercent = this.get('discount.percent');
    return price * (1 - discountPercent);
  }),

  // DEMO[1]: BAD - proto error
  /* discount: {
    couponNotUsed: true,
    percent: 0.1
  }, */

  init() {
    this._super(...arguments);

    // DEMO[1]: GOOD - proto error
    this.set('discount', {
      couponNotUsed: true,
      percent: 0.1
    });
    /* you may notice that this.discount = { } works fine here
    this is ONLY possible in the init hook. Properties have their "finalized" values and become observable
    after all of the init()s have run. 
    Using this.discount = {} is a refactoring problem waiting to happen, because if you move that line to 
    a didInsertElement or some other hook, you will now be circumventing the KVO api.
    */
  },

  actions: {
    applyCoupon() {
      const discountedPrice = this.get('discountedPrice');
      this.set('isCouponApplied', true);
      this.set('discount.couponNotUsed', false);
      this.set('price', discountedPrice);
    }
  }
});

controllers.application.js

import Controller from '@ember/controller';
import { get, set, computed, observer } from '@ember/object';

export default Controller.extend({
  // DEMO[3]: BAD - Observer vs computed properties
  /* amountSavedObs: observer('model.cartItems.@each.{originalPrice,price,qty}', function() {
    console.log('totalSavings - Observer');
    // TODO: can we listen to `isOnSale` as well, to amplify the problem with observer ?
    let _totalAmountSaved = 0;
    const cartItems = get(this, 'model.cartItems');
    cartItems.forEach(item => {
      _totalAmountSaved += (item.originalPrice - item.price) * item.qty;
    });
    _totalAmountSaved = _totalAmountSaved.toFixed(2);
    this.set('totalSavings', _totalAmountSaved);
  }), */

  // DEMO[3]: GOOD - Observer vs computed properties
  totalSavings: computed('model.cartItems.@each.{originalPrice,price,qty}', function() {
    console.log('totalSavings - Computed Property');
    let _totalAmountSaved = 0;
    const cartItems = get(this, 'model.cartItems');
    cartItems.forEach(item => {
      _totalAmountSaved += (item.originalPrice - item.price) * item.qty;
    });
    _totalAmountSaved = _totalAmountSaved.toFixed(2);
    return _totalAmountSaved;
  }),

  totalAmount: computed('model.cartItems.@each.{qty,price}', function() {
    const cartItems = get(this, 'model.cartItems');
    let _totalAmount = 0;
    cartItems.forEach(item => (_totalAmount += item.qty * item.price));
    return _totalAmount;
  }),

  // DEMO[2.2]: BAD - listening to `model.cartItems.[]` vs `model.cartItems`
  /* uniqueChocolatesCount: computed('model.cartItems', function() {
    return this.get('model.cartItems.length');
  }), */

  // DEMO[2.2]: GOOD - listening to `model.cartItems.[]` vs `model.cartItems`
  uniqueChocolatesCount: computed('model.cartItems.[]', function() {
    return this.get('model.cartItems.length');
  }),

  actions: {
    addToCart(candyId) {
      const cartItems = get(this, 'model.cartItems');
      const targetCandy = cartItems.findBy('id', candyId);

      if (targetCandy) {
        const qty = get(targetCandy, 'qty');
        set(targetCandy, 'qty', qty + 1);
      } else {
        const catalogue = get(this, 'model.candies');
        const newCandyLineItem = catalogue.findBy('id', candyId);
        set(newCandyLineItem, 'qty', 1);

        // DEMO[2.1]: BAD - KVO
        /* cartItems.push(newCandyLineItem);
        console.log(cartItems); */

        // DEMO[2.1]: GOOD - KVO
        cartItems.pushObject(newCandyLineItem);
      }
    },

    resetCart() {
      this.set('model.cartItems', []);
    }
  }
});

routes.application.js

import Route from '@ember/routing/route';

export default Route.extend({
  model() {
    this._super(...arguments);

    return {
      candies: [
        {
          id: '1',
          name: 'Ferrero',
          url: 'http://i64.tinypic.com/mjn2h5.jpg',
          price: 10,
          originalPrice: 10,
          isOnSale: true
        },
        {
          id: '2',
          name: 'Lindt',
          url: 'http://i65.tinypic.com/14btfrr.png',
          price: 8,
          originalPrice: 8,
          isOnSale: false
        },
        {
          id: '3',
          name: 'Hersheys',
          url: 'http://i68.tinypic.com/2vtbi3m.jpg',
          price: 8,
          originalPrice: 8,
          isOnSale: true
        },
        {
          id: '4',
          name: 'Kisses',
          url: 'http://i64.tinypic.com/2vnm7bm.png',
          price: 10,
          originalPrice: 10,
          isOnSale: false
        }
      ],

      cartItems: []
    };
  }
});

styles.app.css

body {
  font-family: Arial, Helvetica, sans-serif;
  background-color: #f5f5f5; }

.app-name {
  font-family: -apple-system, system-ui, BlinkMacSystemFont, Segoe UI, Roboto, Helvetica Neue, Fira Sans, Ubuntu, Oxygen, Oxygen Sans, Cantarell, Droid Sans, Apple Color Emoji, Segoe UI Emoji, Segoe UI Emoji, Segoe UI Symbol, Lucida Grande, Helvetica, Arial, sans-serif;
  font-size: 20px;
  line-height: 28px;
  font-weight: 400;
  color: #000000e6; }

.ember-application {
  padding: 20px; }

.catalogue {
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 20px; }

.rounded-border {
  border-radius: 100%; }

.candy-list {
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 20px; }
  .candy-list .candy-item {
    background-color: #fff;
    border: 1px solid #efefef;
    padding: 10px;
    box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.15), 0 4px 6px rgba(0, 0, 0, 0.2);
    transition: box-shadow 83ms; }
    .candy-list .candy-item:hover {
      box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.15), 0 8px 12px rgba(0, 0, 0, 0.2); }
  .candy-list .btn-coupon {
    padding: 4px 12px;
    cursor: pointer;
    background-color: #ef7e37;
    color: #fff;
    text-transform: capitalize;
    border-radius: 5px; }
  .candy-list .btn-cart {
    padding: 4px 12px;
    cursor: pointer;
    background-color: #0073b1;
    font-weight: 800;
    color: #fff;
    text-transform: capitalize; }
  .candy-list .candy-image {
    width: 150px;
    height: 150px;
    border: 2px solid rgba(255, 255, 255, 0.4); }
  .candy-list .candy-footer {
    display: flex;
    justify-content: space-between; }

.cart {
  background-color: #fff;
  min-height: 200px;
  padding: 12px;
  box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.15), 0 4px 6px rgba(0, 0, 0, 0.2); }
  .cart tbody tr:last-child td {
    padding-bottom: 40px; }
  .cart td {
    min-width: 100px; }
  .cart .cart-title {
    font-family: -apple-system, system-ui, BlinkMacSystemFont, Segoe UI, Roboto, Helvetica Neue, Fira Sans, Ubuntu, Oxygen, Oxygen Sans, Cantarell, Droid Sans, Apple Color Emoji, Segoe UI Emoji, Segoe UI Emoji, Segoe UI Symbol, Lucida Grande, Helvetica, Arial, sans-serif;
    font-size: 18px;
    line-height: 28px;
    color: #000000e6;
    margin-bottom: 20px;
    text-align: left; }

th,
td {
  text-align: left; }

.btn-reset-cart {
  padding: 4px 12px;
  cursor: pointer;
  background-color: #900021;
  color: #fff;
  text-transform: capitalize; }

.flex {
  display: flex; }

.text-center {
  text-align: center; }

.text-left {
  text-align: left; }

/*# sourceMappingURL=candyshop.css.map */

templates.application.hbs

<section class="catalogue text-center">
  <h1 class="app-name">Welcome to the Candy Shop</h1>
  <ul class="candy-list">
    {{#each model.candies as |candy|}}
      {{candy-item
        id=candy.id
        name=candy.name
        price=candy.price
        url=candy.url
        isOnSale=candy.isOnSale
        addToCart=(action "addToCart") }}
    {{/each}}
  </ul>
</section>
<section class="cart">
  <table>
    <caption class="cart-title">Shopping Cart</caption>
    <tbody>
      <tr>
        <th>Name</th>
        <th>Price</th>
        <th>Qty</th>
      </tr>
      {{#if model.cartItems.length }}
        {{#each model.cartItems as |item|}}
          <tr>
            <td class="name">{{item.name}}</td>
            <td class="price">{{item.price}}</td>
            <td class="qty">{{item.qty}}</td>
          </tr>
        {{/each}}
      {{else}}
        <tr>
          <td>cart is empty</td>
        </tr>
      {{/if}}
    </tbody>
    <tfoot>
      <tr>
        <td>Total Amount:</td>
        <td>{{totalAmount}}</td>
      </tr>
      <tr>
        <td>Total Savings:</td>
        <td>{{totalSavings}}</td>
      </tr>
      <tr>
        <td>Unique Chocolates Count:</td>
        <td>{{uniqueChocolatesCount}}</td>
      </tr>
    </tfoot>
  </table>
  {{#if model.cartItems.length }}
    <button {{action "resetCart"}} class="btn-reset-cart">Empty Cart</button>
  {{/if}}
</section>
{{outlet}}

templates.components.candy-item.hbs

<section>
  <header class="candy-name text-left">
    {{name}}
    {{#if isDiscountAllowed}}
      <button class="btn-coupon" {{action "applyCoupon"}}>use coupon</button>
    {{/if}}
  </header>
  <img src= {{url}} alt="candy image" class="rounded-border candy-image" />
  <footer class="candy-footer">
    {{#if isCouponApplied}}
      <span class="price">${{discountedPrice}}</span>
    {{else}}
      <span class="price">${{price}}</span>
    {{/if}}
    <button {{action addToCart id}} class="btn-cart">add to cart</button>
  </footer>
</section>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}