Question

我的angular2应用程序中有一个简单的组件：

@Component({
  selector: 'app-product',
  templateUrl: './product.component.html',
  styleUrls: ['./product.component.css'],
  providers: [ProductService, CardService]
})
export class ProductComponent implements OnInit {
  private products;

  constructor(private productService: ProductService, private cartService: CartService) {
  }

  ngOnInit() {
    this.loadProducts();
  }

  loadProducts() {
    this.productService.getProducts().subscribe(data => this.products = data);
  }

  addProductToCart(product: Product) {
    this.cartService.addProduct(product);
  }

  basketAmount() {
    this.cartService.getNumberOfProducts();
  }

连接到它的

html文件：

<div class="basket">
  On your card: {{basketAmount()}}
</div>

<table class="table table-striped">
  <thead class="thead-inverse">
  <tr>
    <th>#</th>
    <th>Name</th>
    <th>Desc</th>
    <th>Price</th>
    <th>Amount</th>
  </tr>
  </thead>
  <tbody *ngFor="let product of products">
  <tr>
    <th scope="row">{{product.id}}</th>
    <td>{{product.name}}</td>
    <td>{{product.description}}</td>
    <td>{{product.price}}</td>
    <td>{{product.amount}}</td>
    <button type="button" class="btn btn-success" (click)="addProductToCart(product)">Add to cart</button>
  </tr>
  </tbody>
</table>

和CartService

@Injectable()
export class CardService {
  private cart: Product[] = [];

  constructor() {
  }

  addProduct(product: Product) {
    this.cart.push(product);
  }

  getTotalPrice() {
    const totalPrice = this.cart.reduce((sum, cardItem) => {
      return sum += cardItem.price, sum;
    }, 0);
    return totalPrice;
  }

  getNumberOfProducts() {
    const totalAmount = this.card.reduce((sum, cardItem) => {
      return sum += cardItem.amount, sum;
    }, 0);
    return totalAmount;
  }
}

export interface Product {
  id: number;
  name: string;
  description: string;
  price: number;
  amount: number;
}

我想在将某些东西放入购物车并在视图上显示之后更新购物车上的商品数量。我通过点击添加商品到购物车并调用addProductToCart方法。同时，我希望按basketAmount()中定义的CartService更新这些项目，并返回购物车上的项目数量。我想我应该以某种方式触发这个basketAmount()方法，但我不知道如何。如何以一种好的方式做到这一点？

Answer 1

您有多个选项

在购物车中推送商品后，再次调用basketAmount方法，您应该有新值。
您可以使用BehaviorSubject。在这种情况下，您只需订阅它，每次您将项目推送到购物车时它将自动更新您的购物车。

Answer 2

好的，我找到了解决方案。我将一个简单的numberOfItems变量添加到ProductComponent：

export class ProductComponent implements OnInit {
  private products;
  private numberOfItems;

  constructor(private productService: ProductService, private cardService: CardService) {
  }

  ngOnInit() {
    this.loadProducts();
  }

  loadProducts() {
    this.productService.getProducts().subscribe(data => this.products = data);
  }

  addProductToCard(product: Product) {
    this.cardService.addProduct(product);
  }

  basketAmount() {
    this.numberOfItems = this.cardService.getNumberOfProducts();
  }
}

在视图中我点击并更新numberOfItems后调用两个方法：

  <div class="basket">
     On your card: {{numberOfItems}}
    </div>

    <table class="table table-striped">
      <thead class="thead-inverse">
      <tr>
        <th>#</th>
    <th>Name</th>
    <th>Desc</th>
    <th>Price</th>
    <th>Amount</th>
      </tr>
      </thead>
      <tbody *ngFor="let product of products">
      <tr>
        <th scope="row">{{product.id}}</th>
        <td>{{product.name}}</td>
        <td>{{product.description}}</td>
        <td>{{product.price}}</td>
        <td>{{product.amount}}</td>
        <button type="button" class="btn btn-success" (click)="addProductToCard(product); basketAmount()">Add to card</button>
      </tr>
      </tbody>
    </table>

Angular2 - 模型更改后的调用方法

2 个答案: