Angular ngbTypeahead给出[Object]错误

<input type="text" [(ngModel)]="searchText" [ngbTypeahead]="search" [ngbTypeaheadSelectItem]="name">

import { Component } from '@angular/core';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';

@Component({
  selector: 'app-search',
  templateUrl: './search.component.html',
  styleUrls: ['./search.component.css']
})
export class SearchComponent {
  searchText: string;

  search = (text$: Observable<string>) =>
    text$.pipe(
      map(term => this.searchData(term))
    );

  searchData(term: string): string[] {
    // Perform search and return an array of strings
    // based on the term
    return ['Result 1', 'Result 2', 'Result 3'];
  }
}