Angular-Docs-Cn/aio/content/getting-started/data.md

Managing Data

管理数据

At the end of Routing, the online store application has a product catalog with two views: a product list and product details. Users can click on a product name from the list to see details in a new view, with a distinct URL (route).

在路由的末尾，本应用实现了一个包含两个视图的商品名录：商品列表和商品详情。用户点击清单中的某个商品名称，就会在新视图中看到具有显著 URL（路由）的详情页。

In this section, you'll create the shopping cart. You'll:

在本节中，你将创建购物车。你将：

• Update the product details page to include a "Buy" button, which adds the current product to a list of products managed by a cart service.

  修改商品详情页，让它包含一个 “Buy” 按钮，它会把当前商品添加到由 "购物车服务" 管理的商品列表中。

• Add a cart component, which displays the items you added to your cart.

  添加一个购物车组件，它会显示你添加到购物车中的商品。

• Add a shipping component, which retrieves shipping prices for the items in the cart by using Angular's HttpClient to retrieve shipping data from a .json file.

  添加一个配送组件，它会使用 Angular 的 HttpClient 从 .json 文件中检索配送数据来取得购物车中这些商品的运费。

{@a services}

Services

服务

Services are an integral part of Angular applications. In Angular, a service is an instance of a class that can be made available to any part of your application using Angular's dependency injection system.

服务是 Angular 应用的重要组成部分。在 Angular 中，服务是一个类的实例，它可以借助 Angular 的依赖注入系统来让应用中的任何一个部件都能使用它。

Services are the place where you share data between parts of your application. For the online store, the cart service is where you store your cart data and methods.

服务可以让你在应用的各个部件之间共享数据。对于在线商店，购物车服务就是存放购物车的数据和方法的地方。

{@a create-cart-service}

Create the shopping cart service

创建购物车服务

Up to this point, users can view product information, and simulate sharing and being notified about product changes. They cannot, however, buy products.

到目前为止，用户可以查看商品信息、模拟共享，并接收商品变化的通知。但是，无法购买商品。

In this section, you'll add a "Buy" button the product details page. You'll also set up a cart service to store information about products in the cart.

在本节中，你将在商品详情页中添加“Buy”按钮。你还可以设置一个购物车服务来存储购物车中商品的相关信息。

Later, in the Forms part of this tutorial, this cart service also will be accessed from the page where the user checks out.

稍后，在本教程的表单部分，也会从用户的结账页面中访问这个 购物车服务。

{@a generate-cart-service}

Define a cart service

定义购物车服务

1. Generate a cart service.

   生成购物车服务。

   1. Right click on the app folder, choose Angular Generator, and choose **Service**. Name the new service cart.

      右键单击 app 文件夹，选择 Angular Generator，然后选择 **Service**。把新的服务命名为 cart。

   2. If the generated @Injectable() decorator does not include the { providedIn: 'root' } statement, then insert it as shown above.

      如果生成的 @Injectable() 装饰器中没有包含 { providedIn: 'root' } 语句，那就插入它，如上图所示。

2. In the CartService class, define an items property to store the list (array) of the current products in the cart.

   在 CartService 类中，定义一个 items 属性来把当前商品的列表（数组）存储在购物车中。

3. Define methods to add items to the cart, return cart items, and clear the cart items:

   定义把商品添加到购物车、返回购物车商品以及清除购物车商品的方法：

{@a product-details-use-cart-service}

Use the cart service

使用购物车服务

In this section, you'll update the product details component to use the cart service. You'll add a "Buy" button to the product details view. When the "Buy" button is clicked, you'll use the cart service to add the current product to the cart.

在本节中，你将修改商品详情组件以使用这个购物车服务。你可以在商品详情视图中添加一个“Buy”按钮。单击“Buy”按钮后，你将借助购物车服务来把当前商品添加到购物车中。

1. Open product-details.component.ts.

   打开 product-details.component.ts。

2. Set up the component to be able to use the cart service.

   设置该组件，使其能使用这个购物车服务。

   1. Import the cart service.

      导入购物车服务。

   2. Inject the cart service.

      注入购物车服务。

3. Define the addToCart() method, which adds the current product to the cart.

   定义 addToCart() 方法，该方法会当前商品添加到购物车中。

   The addToCart() method:

   addToCart() 方法：

   • Receives the current product

     收到当前的 product

   • Uses the cart service's #addToCart() method to add the product the cart

     使用购物车服务的 #addToCart() 方法把该商品添加到购物车中

   • Displays a message that the product has been added to the cart

     显示一条 "商品已添加到购物车" 的消息

4. Update the product details template to have a "Buy" button that adds the current product to the cart.

   修改商品详情模板，让它具有一个“Buy”按钮，用于把当前商品添加到购物车中。

   1. Open product-details.component.html.

      打开 product-details.component.html。

   2. Add a button with the label "Buy", and bind the click() event to the addToCart() method:

      添加一个标签为“Buy”的按钮，并把其 click() 事件绑定到 addToCart() 方法：

5. To see the new "Buy" button, refresh the application and click on a product's name to display its details.

   要查看新的“Buy”按钮，请刷新应用并单击商品名称以显示其详细信息。

   

6. Click the "Buy" button. The product is added to the stored list of items in the cart, and a message is displayed.

   点击“Buy”按钮。该商品已添加到了购物车中存储的商品列表中，并显示一条消息。

   

Create the cart page

创建购物车页面

At this point, users can put items in the cart by clicking "Buy", but they can't yet see their cart.

此时，用户可以通过点击“Buy”来把商品放入购物车，但他们还看不到购物车。

We'll create the cart page in two steps:

我们将分两步来创建购物车页面：

1. Create a cart component and set up routing to the new component. At this point, the cart page will only have default text.

   创建一个购物车组件并设置到这个新组件的路由。此时，购物车页面只会显示默认文本。

2. Display the cart items.

   显示购物车商品

Set up the component

设置该组件

To create the cart page, you begin by following the same steps you did to create the product details component and to set up routing for the new component.

要创建购物车页面，首先要执行与创建商品详情组件相同的步骤，并为这个新组件设置路由。

1. Generate a cart component, named cart.

   生成一个名叫 cart 的购物车组件。

   Reminder: In the file list, right-click the app folder, choose Angular Generator and Component.

   提示：在文件列表框中，右键单击 app 文件夹，选择 Angular Generator 和 Component。

2. Add routing (a URL pattern) for the cart component.

   为购物车组件添加路由（URL 模式）。

   Reminder: Open app.module.ts and add a route for the component CartComponent, with a path of cart:

   提示：打开 app.module.ts，为组件 CartComponent 添加一个路由，其路由为 cart ：

3. To see the new cart component, click the "Checkout" button. You can see the "cart works!" default text, and the URL has the pattern https://getting-started.stackblitz.io/cart, where getting-started.stackblitz.io may be different for your StackBlitz project.

   要查看新的购物车组件，请点击“Checkout”按钮。你会看到默认文本“cart works!”，该 URL 的格式为 https://getting-started.stackblitz.io/cart，其中的 getting-started.stackblitz.io 部分可能与你的 StackBlitz 项目不同。

   (Note: The "Checkout" button that we provided in the top-bar component was already configured with a routerLink for /cart.)

   （注意：我们在顶栏组件中提供的“Checkout”按钮已经配置了指向 /cart 的 routerLink。）

   

Display the cart items

显示购物车商品

Services can be used to share data across components:

服务可用于跨组件共享数据：

• The product details component already uses the cart service (CartService) to add products to the cart.

  商品详情组件已经使用了购物车服务（ CartService ）来把商品添加到购物车中。

• In this section, you'll update the cart component to use the cart service to display the products in the cart.

  在本节中，你将修改购物车组件以使用购物车服务来显示购物车中的商品。

1. Open cart.component.ts.

   打开 cart.component.ts。

2. Set up the component to be able to use the cart service. (This is the same way you set up the product details component to use the cart service, above.)

   设置该组件是为了让它能够使用这个购物车服务。（这与你在前面设置商品详情组件以使用购物车服务的方式是一样的。）

   1. Import the CartService from the cart.service.ts file.

      从 cart.service.ts 文件中导入 CartService。

   2. Inject the CartService to manage cart information.

      注入 CartService 来管理购物车信息。

3. Define the items property to store the products in the cart.

   定义 items 属性，以便把商品存放在购物车中。

4. Set the items using the cart service's getItems() method. (You defined this method when you generated cart.service.ts.)

   使用购物车服务的 getItems() 方法设置这些商品。（你在生成 cart.service.ts 时定义过这个方法。）

   The resulting CartComponent class should look like this:

   所生成的 CartComponent 类是这样的：

5. Update the template with a header ("Cart"), and use a <div> with an *ngFor to display each of the cart items with its name and price.

   修改模板，加上标题（“Cart”），用带有 *ngFor 的 <div> 来显示每个购物车商品的名字和价格。

   The resulting CartComponent template should look like this:

   生成的 CartComponent 模板如下：

6. Test your cart component.

   测试你的购物车组件。

   1. Click on "My Store" to go to the product list page.

      点击“My Store”，进入商品列表页面。

   2. Click on a product name to display its details.

      单击商品名称以显示其详细信息。

   3. Click "Buy" to add the product to the cart.

      点击“Buy”，即可将商品添加到购物车。

   4. Click "Checkout" to see the cart.

      点击“Checkout”查看购物车。

   5. To add another product, click "My Store" to return to the product list. Repeat the steps above.

      要添加其它商品，请点击“My Store”返回商品列表。重复上述步骤。

   

StackBlitz tip: Any time the preview refreshes, the cart is cleared. If you make changes to the app, the page refreshes, and you'll need to buy products again to populate the cart.

StackBlitz 提示：只要预览刷新，就会清除购物车。如果你对该应用进行了更改，页面就会刷新，你需要重新购买商品来填充购物车。

Learn more: See Introduction to Services and Dependency Injection for more information about services.

要了解关于服务的更多信息，请参阅“服务和依赖注入简介”。

Retrieve shipping prices

检索运费价格

Data returned from servers often takes the form of a stream. Streams are useful because they make it easy to transform the data that is returned, and to make modifications to the way data is requested. The Angular HTTP client (HttpClient) is a built-in way to fetch data from external APIs and provide them to your application as a stream.

从服务器返回的数据通常采用流的形式。流是很有用的，因为它们可以很容易地转换返回的数据，也可以修改请求数据的方式。Angular 的 HTTP 客户端（ HttpClient ）是一种内置的方式，可以从外部 API 中获取数据，并以流的形式提供给你的应用。

In this section, you'll use the HTTP client to retrieve shipping prices from an external file.

在本节中，你将使用 HTTP 客户端从外部文件中检索运费。

Predefined shipping data

预定义的配送数据

For the purpose of this Getting Started, we have provided shipping data in assets/shipping.json. You'll use this data to add shipping prices for items in the cart.

为了满足本“入门指南”的需求，我们在 assets/shipping.json 中提供了配送数据。你可以利用这些数据为购物车中的商品添加运费。

Enable HttpClient for app

为应用启用 HttpClient

Before you can use Angular's HTTP client, you must set up your app to use HttpClientModule.

在使用 Angular 的 HTTP 客户端之前，你必须先设置你的应用来使用 HttpClientModule。

Angular's HttpClientModule registers the providers needed to use a single instance of the HttpClient service throughout your app. The HttpClient service is what you inject into your services to fetch data and interact with external APIs and resources.

Angular 的 HttpClientModule 中注册了在整个应用中使用 HttpClient 服务的单个实例所需的服务提供商。你可以在服务中注入 HttpClient 服务来获取数据并与外部 API 和资源进行交互。

1. Open app.module.ts.

   打开 app.module.ts。

   This file contains imports and functionality that is available to the entire app.

   该文件包含可供整个应用使用的导入对象和功能。

2. Import HttpClientModule from the @angular/common/http package.

   从 @angular/common/http 包中导入 HttpClientModule。

3. Add HttpClientModule to the imports array of the app module (@NgModule).

   把 HttpClientModule 添加到应用模块（@NgModule）的 imports 数组中。

   This registers Angular's HttpClient providers globally.

   这会在全局注册 Angular 的 HttpClient 提供商。

Enable HttpClient for cart service

为购物车服务启用 HttpClient

1. Open cart.service.ts.

   打开 cart.service.ts。

2. Import HttpClient from the @angular/common/http package.

   从 @angular/common/http 包中导入 HttpClient。

3. Inject HttpClient into the constructor of the CartService component class:

   把 HttpClient 注入到 CartService 组件类的构造函数中：

Define the get() method

定义 get() 方法

As you've seen, multiple components can leverage the same service. Later in this tutorial, the shipping component will use the cart service to retrieve shipping data via HTTP from the shipping.json file. Here you'll define the get() method that will be used.

如你所见，多个组件可以使用同一个服务。在这个教程的后半部分，商品配送组件将使用该购物车服务从 shipping.json 文件中借助 HTTP 检索配送数据。在这里你要定义很快就要用到的 get() 方法。

1. Continue working in cart.service.ts.

   继续在 cart.service.ts 中工作。

2. Below the clearCart() method, define a new getShippingPrices() method that uses the HttpClient#get() method to retrieve the shipping data (types and prices).

   在 clearCart() 方法下面，定义一个新的 getShippingPrices() 方法，该方法使用 HttpClient#get() 方法检索配送数据（类型和价格）。

Learn more: See the HttpClient guide for more information about Angular's HttpClient.

要了解关于 Angular HttpClient 的更多信息，请参阅HttpClient 指南。

Define the shipping page

定义配送页面

Now that your app can retrieve shipping data, you'll create a shipping component and associated template.

现在你的应用已经可以检索配送数据了，你还要创建一个配送组件和相关的模板。

1. Generate a new component named shipping.

   生成一个名为 shipping 的新组件。

   Reminder: In the file list, right-click the app folder, choose Angular Generator and Component.

   提示：在文件列表框中，右键单击 app 文件夹，选择 Angular Generator 和 Component。

2. In app.module.ts, add a route for shipping. Specify a path of shipping and a component of ShippingComponent.

   在 app.module.ts 中，添加一个配送路由。其 path 为 shipping，其 component 为 ShippingComponent。

   The new shipping component isn't hooked into any other component yet, but you can see it in the preview pane by entering the URL specified by its route. The URL has the pattern: https://getting-started.stackblitz.io/shipping where the getting-started.stackblitz.io part may be different for your StackBlitz project.

   新的配送组件尚未挂钩到任何其它组件，但你可以通过输入其路由特有的 URL 在预览窗格中看到它。该 URL 具有以下模式：https://getting-started.stackblitz.io/shipping，其中的 gets-started.stackblitz.io 部分可能与你的 StackBlitz 项目不同。

3. Modify the shipping component so it uses the cart service to retrieve shipping data via HTTP from the shipping.json file.

   修改配送组件，让它利用购物车服务从 shipping.json 文件中通过 HTTP 检索配送数据。

   1. Import the cart service.

      导入购物车服务。

   2. Define a shippingCosts property.

      定义 shippingCosts 属性。

   3. Inject the cart service into the ShippingComponent class:

      把购物车服务注入到 ShippingComponent 类中：

   4. Set the shippingCosts property using the getShippingPrices() method from cart service.

      利用购物车服务的 getShippingPrices() 方法设置 shippingCosts 属性。

4. Update the shipping component's template to display the shipping types and prices using async pipe:

   利用 async 管道修改配送组件的模板，以显示配送类型和价格：

5. Add a link from the cart page to the shipping page:

   在购物车页面中添加一个到配送页面的链接：

6. Test your shipping prices feature:

   测试这个运费价格功能：

   Click on the "Checkout" button to see the updated cart. (Remember that changing the app causes the preview to refresh, which empties the cart.)

   点击“Checkout”按钮，查看更新后的购物车。（注意，修改应用会导致预览窗格刷新，这会清空购物车。）

   

   Click on the link to navigate to the shipping prices.

   点击此链接可以导航到运费页。

   

Next steps

下一步

Congratulations! You have an online store application with a product catalog and shopping cart. You also have the ability to look up and display shipping prices.

恭喜！你有一个带有商品名录和购物车的在线商店应用了，而且你还可以查询并显示运费。

To continue exploring Angular, choose either of the following options:

要继续探索 Angular，请选择下列选项之一：

• Continue to the "Forms" section to finish the app by adding the shopping cart page and a form-based checkout feature. You'll create a form to collect user information as part of checkout.

  继续浏览“表单”部分，通过添加购物车页面和基于表单的结帐功能来完成该应用。你还可以创建一个表单来收集用户信息，作为结账过程的一部分。

• Skip ahead to the "Deployment" section to deploy your app to Firebase or move to local development.

  跳到“部署”部分，把你的应用部署到 Firebase 或转成本地开发。