Angular请求防抖处理第一次请求失效问题

<p-autoComplete [(ngModel)]="text" [suggestions]="results" 
(completeMethod)="search($event)">
</p-autoComplete>

packages$: Observable<NpmPackageInfo[]>;
private searchText$ = new Subject<string>();

search(packageName: string) {
 this.searchText$.next(packageName);
}
ngOnInit() {
 this.packages$ = this.searchText$.pipe(
 debounceTime(500),
 distinctUntilChanged(),
 switchMap(packageName =>
  this.searchService.search(packageName, this.withRefresh))
 );
}

private searchText$ = new Subject<string>();
packages$: Observable<InstrumentAlias[]>;
ngOnInit() {
// 创建可观察着对象
this.packages$ = this.searchText$.pipe(
   debounceTime(500),
   distinctUntilChanged(),
   switchMap(packageName =>
    this.instrumentAliasService.queryInstrumentAliasByName(packageName))
  );
}
this.searchText$.next(this.queryName);
this.packages$.subscribe((instrumentAliases: Array<InstrumentAlias>) => {
 this.filteredinstrumentAlias = instrumentAliases;
}, () => {
 console.log('get instrumentAliases error');
});