使用 @for 在元件中列出物件

本教學課程示範如何在 Angular 範本中使用 @for 區塊，在範本中顯示動態重複的資料。

NOTE: 這部影片反映的是較舊的語法，但主要概念仍然適用。

你將學到什麼

  • 你將為應用程式加入一組資料
  • 你的應用程式會使用 @for 顯示新資料集中的元素清單

@for 概念預覽

在 Angular 中，@for 是一種特定類型的控制流程區塊，用來在範本中動態重複資料。在純 JavaScript 中你會使用 for 迴圈，而 @for 為 Angular 範本提供了類似的功能。

你可以利用 @for 迭代陣列，甚至是非同步值。在這一課中，你會加入一組新的資料陣列來迭代。

如需更深入的說明，請參閱控制流程指南。

  1. 將房屋資料加入 Home

    Home 中目前只有單一房屋地點。在這個步驟中，你會加入一個 HousingLocation 項目陣列。

    1. 在 src/app/home/home.ts 中，從 Home 類別移除 housingLocation 屬性。

    2. 更新 Home 類別，讓它有一個名為 housingLocationList 的屬性。將你的程式碼更新成與下列程式碼一致：

      在 home.ts 中加入 housingLocationList 屬性

      import {Component} from '@angular/core';
import {HousingLocation} from '../housing-location/housing-location';
import {HousingLocationInfo} from '../housinglocation';

@Component({
  selector: 'app-home',
  imports: [HousingLocation],
  template: `
    <section>
      <form>
        <input type="text" placeholder="Filter by city" />
        <button class="primary" type="button">Search</button>
      </form>
    </section>
    <section class="results">
      @for (housingLocation of housingLocationList; track $index) {
        <app-housing-location [housingLocation]="housingLocation" />
      }
    </section>
  `,
  styleUrl: './home.css',
})
export class Home {
  readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';

  housingLocationList: HousingLocationInfo[] = [
    {
      id: 0,
      name: 'Acme Fresh Start Housing',
      city: 'Chicago',
      state: 'IL',
      photo: `${this.baseUrl}/bernard-hermant-CLKGGwIBTaY-unsplash.jpg`,
      availableUnits: 4,
      wifi: true,
      laundry: true,
    },
    {
      id: 1,
      name: 'A113 Transitional Housing',
      city: 'Santa Monica',
      state: 'CA',
      photo: `${this.baseUrl}/brandon-griggs-wR11KBaB86U-unsplash.jpg`,
      availableUnits: 0,
      wifi: false,
      laundry: true,
    },
    {
      id: 2,
      name: 'Warm Beds Housing Support',
      city: 'Juneau',
      state: 'AK',
      photo: `${this.baseUrl}/i-do-nothing-but-love-lAyXdl1-Wmc-unsplash.jpg`,
      availableUnits: 1,
      wifi: false,
      laundry: false,
    },
    {
      id: 3,
      name: 'Homesteady Housing',
      city: 'Chicago',
      state: 'IL',
      photo: `${this.baseUrl}/ian-macdonald-W8z6aiwfi1E-unsplash.jpg`,
      availableUnits: 1,
      wifi: true,
      laundry: false,
    },
    {
      id: 4,
      name: 'Happy Homes Group',
      city: 'Gary',
      state: 'IN',
      photo: `${this.baseUrl}/krzysztof-hepner-978RAXoXnH4-unsplash.jpg`,
      availableUnits: 1,
      wifi: true,
      laundry: false,
    },
    {
      id: 5,
      name: 'Hopeful Apartment Group',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/r-architecture-JvQ0Q5IkeMM-unsplash.jpg`,
      availableUnits: 2,
      wifi: true,
      laundry: true,
    },
    {
      id: 6,
      name: 'Seriously Safe Towns',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/phil-hearing-IYfp2Ixe9nM-unsplash.jpg`,
      availableUnits: 5,
      wifi: true,
      laundry: true,
    },
    {
      id: 7,
      name: 'Hopeful Housing Solutions',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/r-architecture-GGupkreKwxA-unsplash.jpg`,
      availableUnits: 2,
      wifi: true,
      laundry: true,
    },
    {
      id: 8,
      name: 'Seriously Safe Towns',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/saru-robert-9rP3mxf8qWI-unsplash.jpg`,
      availableUnits: 10,
      wifi: false,
      laundry: false,
    },
    {
      id: 9,
      name: 'Capital Safe Towns',
      city: 'Portland',
      state: 'OR',
      photo: `${this.baseUrl}/webaliser-_TPTXZd9mOo-unsplash.jpg`,
      availableUnits: 6,
      wifi: true,
      laundry: true,
    },
  ];
}

      IMPORTANT: 不要移除 @Component 裝飾器，你會在接下來的步驟中更新那段程式碼。

  2. 更新 Home 範本，改用 @for

    現在應用程式有一組資料集，你可以使用 @for 區塊在瀏覽器中顯示其中的項目。

    1. 將範本程式碼中的 <app-housing-location> 標籤更新成這樣：

      在 home.ts 的 Home 範本中加入 @for

      import {Component} from '@angular/core';
import {HousingLocation} from '../housing-location/housing-location';
import {HousingLocationInfo} from '../housinglocation';

@Component({
  selector: 'app-home',
  imports: [HousingLocation],
  template: `
    <section>
      <form>
        <input type="text" placeholder="Filter by city" />
        <button class="primary" type="button">Search</button>
      </form>
    </section>
    <section class="results">
      @for (housingLocation of housingLocationList; track $index) {
        <app-housing-location [housingLocation]="housingLocation" />
      }
    </section>
  `,
  styleUrl: './home.css',
})
export class Home {
  readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';

  housingLocationList: HousingLocationInfo[] = [
    {
      id: 0,
      name: 'Acme Fresh Start Housing',
      city: 'Chicago',
      state: 'IL',
      photo: `${this.baseUrl}/bernard-hermant-CLKGGwIBTaY-unsplash.jpg`,
      availableUnits: 4,
      wifi: true,
      laundry: true,
    },
    {
      id: 1,
      name: 'A113 Transitional Housing',
      city: 'Santa Monica',
      state: 'CA',
      photo: `${this.baseUrl}/brandon-griggs-wR11KBaB86U-unsplash.jpg`,
      availableUnits: 0,
      wifi: false,
      laundry: true,
    },
    {
      id: 2,
      name: 'Warm Beds Housing Support',
      city: 'Juneau',
      state: 'AK',
      photo: `${this.baseUrl}/i-do-nothing-but-love-lAyXdl1-Wmc-unsplash.jpg`,
      availableUnits: 1,
      wifi: false,
      laundry: false,
    },
    {
      id: 3,
      name: 'Homesteady Housing',
      city: 'Chicago',
      state: 'IL',
      photo: `${this.baseUrl}/ian-macdonald-W8z6aiwfi1E-unsplash.jpg`,
      availableUnits: 1,
      wifi: true,
      laundry: false,
    },
    {
      id: 4,
      name: 'Happy Homes Group',
      city: 'Gary',
      state: 'IN',
      photo: `${this.baseUrl}/krzysztof-hepner-978RAXoXnH4-unsplash.jpg`,
      availableUnits: 1,
      wifi: true,
      laundry: false,
    },
    {
      id: 5,
      name: 'Hopeful Apartment Group',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/r-architecture-JvQ0Q5IkeMM-unsplash.jpg`,
      availableUnits: 2,
      wifi: true,
      laundry: true,
    },
    {
      id: 6,
      name: 'Seriously Safe Towns',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/phil-hearing-IYfp2Ixe9nM-unsplash.jpg`,
      availableUnits: 5,
      wifi: true,
      laundry: true,
    },
    {
      id: 7,
      name: 'Hopeful Housing Solutions',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/r-architecture-GGupkreKwxA-unsplash.jpg`,
      availableUnits: 2,
      wifi: true,
      laundry: true,
    },
    {
      id: 8,
      name: 'Seriously Safe Towns',
      city: 'Oakland',
      state: 'CA',
      photo: `${this.baseUrl}/saru-robert-9rP3mxf8qWI-unsplash.jpg`,
      availableUnits: 10,
      wifi: false,
      laundry: false,
    },
    {
      id: 9,
      name: 'Capital Safe Towns',
      city: 'Portland',
      state: 'OR',
      photo: `${this.baseUrl}/webaliser-_TPTXZd9mOo-unsplash.jpg`,
      availableUnits: 6,
      wifi: true,
      laundry: true,
    },
  ];
}

      請注意，在程式碼 [housingLocation] = "housingLocation" 中，housingLocation 值現在指的是 @for 區塊中使用的變數。在這次變更之前，它指的是 Home 類別上的屬性。

    2. 儲存所有變更。

    3. 重新整理瀏覽器，確認應用程式現在會渲染出房屋地點的格狀清單。

    homes-app 的瀏覽器畫面，顯示標誌、篩選文字輸入框、搜尋按鈕與房屋地點卡片格狀清單

SUMMARY: 在這一課中，你使用 @for 區塊在 Angular 範本中動態重複資料。你也為 Angular 應用程式加入了一組新的資料陣列。應用程式現在會在瀏覽器中動態渲染房屋地點清單。

應用程式逐漸成形，做得很好。

如需本課所涵蓋主題的更多資訊，請造訪：