Angular rxjs映射管道给出了“此”上下文问题

Question

I Just upgraded a CLI project to use angular 6+ Everything works just fine and the site shows data as excepted.. so no problems except for 1 small issue...

The 'this' context of type 'Observable' is not assignable to method's 'this' of type 'Observable<[Category, ProductList]>'.

getStartpageCategoryWithProducts(startpagePosition, pageSize ?, page ?): Promise < [Category, ProductList] > {
  let params = new HttpParams();
  if(pageSize) { params = params.append('pageSize', pageSize); }
    if(page) { params = params.append('page', page); }
    const options = {
    params
  };
  const url = 'catalog/categories/startpagePosition/' + startpagePosition;
  return this.http.get(url, options).pipe(
    map(res => [res['category'], this.extractData(res['searchResult'])]),
    catchError((err) => this.handleError(err))
  ).toPromise<[Category, ProductList]>();
}

Answer 1

I think the problem is .get.map is not giving you an Observable<[Category, ProductList]> but just a plain Observable, you would be fine if you just remove the typing in toPromise

getStartpageCategoryWithProducts(startpagePosition, pageSize ?, page ?): Promise {
  let params = new HttpParams();
  if(pageSize) { params = params.append('pageSize', pageSize); }
    if(page) { params = params.append('page', page); }
    const options = {
    params
  };
  const url = 'catalog/categories/startpagePosition/' + startpagePosition;
  return this.http.get(url, options).pipe(
    map(res => [res['category'], this.extractData(res['searchResult'])]),
    catchError((err) => this.handleError(err))
  ).toPromise();
}