如何在Angular 7中创建延迟加载Treeview

Question

我正在使用Angular创建TreeView，并且创建Treeview的场景是每个级别都有不同的API，这意味着如果我单击父级别节点之一，则仅子节点应该只为该特定节点生成，依此类推，对于进一步的级别，每个子节点列表都来自API

现在的问题是，当我在任何节点上单击时，正在为创建的树视图创建嵌套列表时。子节点正在为该节点以及其他节点生成。

这是我的代码。

<ul>
    <li *ngFor="let item of companyList" [id]="item.id">
        <span (click)="getLocation(item)">{{item.description}}</span>
      <ul>
          <li *ngFor="let loc of loactionData" [id]="loc.id">
          <span (click)="getDepartment(loc)">{{loc.description}}</span>
          <ul>
            <li *ngFor="let depart of deaprtmentData">
              <span (click)="getEmpStatus(depart)">{{depart.description}}</span>
            </li>
           </ul>
          </li>
    </ul>
  </li>
</ul>

注意：每个列表都来自单独的API，这些click事件有助于调用API。

请帮助我解决上述问题，谢谢。

Answer 1

您正在为每个nesting重复相同的嵌套列表ul。您必须将嵌套列表与他们的父母相关联。

由于您的companyList项目和locationData项目具有ID，因此请使用此ID将嵌套列表与每个公司和每个位置相关联。

要进行关联，请使用简单的对象在代码中创建一个地图，然后使用索引签名键入它。在您的情况下，它将如下所示：

companyList: Company[] = [];
locationData: { [companyId: string]: Location[] } = {};
departmentData: { [locationId: string]: Department[] } = {};

然后，在模板中，您需要索引locationData并departmentData使用item.id和loc.id：

<ul>
  <li *ngFor="let item of companyList" [id]="item.id">
    <span (click)="getLocation(item)">{{ item.description }}</span>
    <ul>
      <li *ngFor="let loc of locationData[item.id]" [id]="loc.id">
        <span (click)="getDepartment(loc)">{{ loc.description }}</span>
        <ul>
          <li *ngFor="let depart of departmentData[loc.id]">
            <span (click)="getEmpStatus(depart)">{{ depart.description }}</span>
          </li>
        </ul>
      </li>
    </ul>
  </li>
</ul>

生成数据时，请将其放在对象中正确的ID下：

getLocation(item: Company): void {
  this.http.get<Location[]>(`${this.api}/locations?companyId=${item.id}`).subscribe(locations => {
    this.locationData[item.id] = locations;
  })
}

getDepartment(location: Location): void {
  this.http.get<Department[]>(`${this.api}/departments?locationId=${location.id}`).subscribe(departments => {
    this.departmentData[location.id] = departments;
  })
}

这是一个带有用户/帖子/评论数据模型和jsonplaceholderAPI 的示例。

观看此Stackblitz演示以获取实时示例

<ul>
  <li *ngFor="let user of users" [id]="user.id">
    <span (click)="getPosts(user)">{{ user.name }}</span>
    <ul>
      <li *ngFor="let post of posts[user.id]" [id]="post.id">
        <span (click)="getComments(post)">{{ post.title }}</span>
        <ul>
          <li *ngFor="let comment of comments[post.id]">
            <span>{{ comment.name }}</span>
          </li>
        </ul>
      </li>
    </ul>
  </li>
</ul>

import { Component, OnInit } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, of } from 'rxjs';

interface User {
  id: number;
  name: string;
  username: string;
  email: string;
}

interface Post {
  userId: number;
  id: number;
  title: string;
  body: string;
}

interface Comment {
  postId: number;
  id: number;
  name: string;
  email: string;
  body: string;
}

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements OnInit {
  users: User[] = [];
  posts: { [id: number]: Post[] } = {};
  comments: { [id: number]: Comment[] } = {};

  private api = 'https://jsonplaceholder.typicode.com';

  constructor(private http: HttpClient) { }

  ngOnInit(): void {
    this.http.get<User[]>(`${this.api}/users`).subscribe(users => this.users = users);
  }

  getPosts(user: User): void {
    this.http.get<Post[]>(`${this.api}/posts?userId=${user.id}`).subscribe(posts => {
      this.posts[user.id] = posts;
    })
  }

  getComments(post: Post): void {
    this.http.get<Comment[]>(`${this.api}/comments?postId=${post.id}`).subscribe(comments => {
      this.comments[post.id] = comments;
    })
  }
}