如何在異步httpclient調用中使用ngx-bootstrap typeahead

Question

我正在嘗試使用來自Angular 4中的休息后端的異步結果填充nxg-bootstrap typeahead。他們的站點有一個示例（ https://valor-software.com/ngx-bootstrap/#/typeahead ）如何執行此操作使用模擬可觀察數據，但我正在努力使用httpclient。 使用它的人的所有示例都使用舊的Http模塊而不是Angular 4中使用的新HttpClient模塊。

這是他們的例子：

import { Component } from '@angular/core';

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
import { TypeaheadMatch } from 'ngx-bootstrap/typeahead';

@Component({
  selector: 'demo-typeahead-async',
  templateUrl: './async.html'
})
export class DemoTypeaheadAsyncComponent {
  asyncSelected: string;
  typeaheadLoading: boolean;
  typeaheadNoResults: boolean;
  dataSource: Observable<any>;
  statesComplex: any[] = [
    { id: 1, name: 'Alabama', region: 'South' },
    { id: 2, name: 'Alaska', region: 'West' },
    {
      id: 3,
      name: 'Arizona',
      region: 'West'
    },
    { id: 4, name: 'Arkansas', region: 'South' },
    { id: 5, name: 'California', region: 'West' },
    { id: 6, name: 'Colorado', region: 'West' },
    { id: 7, name: 'Connecticut', region: 'Northeast' },
    { id: 8, name: 'Delaware', region: 'South' },
    { id: 9, name: 'Florida', region: 'South' },
    { id: 10, name: 'Georgia', region: 'South' },
    { id: 11, name: 'Hawaii', region: 'West' },
    { id: 12, name: 'Idaho', region: 'West' },
    { id: 13, name: 'Illinois', region: 'Midwest' },
    { id: 14, name: 'Indiana', region: 'Midwest' },
    { id: 15, name: 'Iowa', region: 'Midwest' },
    { id: 16, name: 'Kansas', region: 'Midwest' },
    { id: 17, name: 'Kentucky', region: 'South' },
    { id: 18, name: 'Louisiana', region: 'South' },
    { id: 19, name: 'Maine', region: 'Northeast' },
    { id: 21, name: 'Maryland', region: 'South' },
    { id: 22, name: 'Massachusetts', region: 'Northeast' },
    { id: 23, name: 'Michigan', region: 'Midwest' },
    { id: 24, name: 'Minnesota', region: 'Midwest' },
    { id: 25, name: 'Mississippi', region: 'South' },
    { id: 26, name: 'Missouri', region: 'Midwest' },
    { id: 27, name: 'Montana', region: 'West' },
    { id: 28, name: 'Nebraska', region: 'Midwest' },
    { id: 29, name: 'Nevada', region: 'West' },
    { id: 30, name: 'New Hampshire', region: 'Northeast' },
    { id: 31, name: 'New Jersey', region: 'Northeast' },
    { id: 32, name: 'New Mexico', region: 'West' },
    { id: 33, name: 'New York', region: 'Northeast' },
    { id: 34, name: 'North Dakota', region: 'Midwest' },
    { id: 35, name: 'North Carolina', region: 'South' },
    { id: 36, name: 'Ohio', region: 'Midwest' },
    { id: 37, name: 'Oklahoma', region: 'South' },
    { id: 38, name: 'Oregon', region: 'West' },
    { id: 39, name: 'Pennsylvania', region: 'Northeast' },
    { id: 40, name: 'Rhode Island', region: 'Northeast' },
    { id: 41, name: 'South Carolina', region: 'South' },
    { id: 42, name: 'South Dakota', region: 'Midwest' },
    { id: 43, name: 'Tennessee', region: 'South' },
    { id: 44, name: 'Texas', region: 'South' },
    { id: 45, name: 'Utah', region: 'West' },
    { id: 46, name: 'Vermont', region: 'Northeast' },
    { id: 47, name: 'Virginia', region: 'South' },
    { id: 48, name: 'Washington', region: 'South' },
    { id: 49, name: 'West Virginia', region: 'South' },
    { id: 50, name: 'Wisconsin', region: 'Midwest' },
    { id: 51, name: 'Wyoming', region: 'West' }
  ];

  constructor() {
    this.dataSource = Observable.create((observer: any) => {
      // Runs on every search
      observer.next(this.asyncSelected);
    }).mergeMap((token: string) => this.getStatesAsObservable(token));
  }

  getStatesAsObservable(token: string): Observable<any> {
    let query = new RegExp(token, 'ig');

    return Observable.of(
      this.statesComplex.filter((state: any) => {
        return query.test(state.name);
      })
    );
  }

  changeTypeaheadLoading(e: boolean): void {
    this.typeaheadLoading = e;
  }

  changeTypeaheadNoResults(e: boolean): void {
    this.typeaheadNoResults = e;
  }

  typeaheadOnSelect(e: TypeaheadMatch): void {
    console.log('Selected value: ', e.value);
  }
}

用模板

<pre class="card card-block card-header">Model: {{asyncSelected | json}}
</pre>
  <input [(ngModel)]="asyncSelected"
         [typeahead]="dataSource"
         (typeaheadLoading)="changeTypeaheadLoading($event)"
         (typeaheadNoResults)="changeTypeaheadNoResults($event)"
         (typeaheadOnSelect)="typeaheadOnSelect($event)"
         [typeaheadOptionsLimit]="7"
         typeaheadOptionField="name"
         placeholder="Locations loaded with timeout"
         class="form-control">
  <div *ngIf="typeaheadLoading===true">Loading</div>
  <div *ngIf="typeaheadNoResults===true">&#10060; No Results Found</div>

這是我嘗試的唯一一個無法工作的部分：

this.dataSource = Observable.create((observer: any) => {
    // Runs on every search
    observer.next(this.typeAheadResult);
    }).mergeMap((token: string) => {  
        return this.httpClient.get<string[]>(`${this.typeAheadUrl}?q=${token}`);              
    });

通常情況下，對於這樣的通話，我會做類似的事情：

this.httpClient.get<string[]>(`${this.typeAheadUrl}?q=${token}`)
    .subscribe(results => this.results = results)

但這不太正確

Answer 1

這是解決方案，它可能有一些寫得不好或冗余的代碼（尤其是.map(r => r) ），它向我看，也許它可以簡化，但是用HttpClient獲取異步結果，這個將工作：

this.dataSource = Observable.create((observer: any) => {
    // Runs on every search
    observer.next(this.typeAheadResult);
    }).mergeMap((token: string) => {  
        return this.httpClient.get<string[]>(`${this.typeAheadUrl}?q=${token}`).map(r => r);              
    });

Answer 2

我這樣做了：

this.dataSource = Observable.create((observer: Observer<any[]>) => {
        this.httpClient.get<string[]>(`${this.typeAheadUrl}?q=${token}`).subscribe((responseItems: any[]) => {
            observer.next(responseItems);
        });
      });

這是有效的，如果您必須檢查某些條件是否已滿，以發送請求，這很有趣，例如，檢查輸入字段是否已被聚焦。 如果您不需要做任何類似的事情，這更簡單：

this.dataSource = this.httpClient.get<string[]>(`${this.typeAheadUrl}?q=${token}`);