Angular 4/5 HttpClient : Argument of type string is not assignable to 'body'

Question

Angular 文档说:

The response body doesn't return all the data you may need. Sometimes servers return special headers or status codes to indicate certain conditions, and inspecting those can be necessary. To do this, you can tell HttpClient you want the full response instead of just the body with the observe option:

http
  .get<MyJsonData>('/data.json', {observe: 'response'})
  .subscribe(resp => {
    // Here, resp is of type HttpResponse<MyJsonData>.
    // You can inspect its headers:
    console.log(resp.headers.get('X-Custom-Header'));
    // And access the body directly, which is typed as MyJsonData as requested.
    console.log(resp.body.someField);
  });

但是当我尝试这样做时，出现编译时错误(虽然没有运行时错误，但按预期工作):

error TS2345: Argument of type '{ headers: HttpHeaders; observe: string; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'. Types of property 'observe' are incompatible. Type 'string' is not assignable to type '"body"'.

为什么？我使用 "@angular/http": "^5.1.0"

这是我的代码版本:

  login(credentials: Credentials): Observable<any> {
    const options = {
      headers: new HttpHeaders({'Content-Type': 'application/json'}),
      observe: 'response'
    };
    return this.httpClient.post<any>(`${environment.USER_SERVICE_BASE_URL}`,
      {'username': credentials.username, 'password': credentials.password}, options)
      .map((res) => ...

Answer 1

您必须内联选项。参见 github ticket #18586 , alxhub 于 8 月 9 日发表 2017.

Typescript needs to be able to infer the observe and responseType values statically, in order to choose the correct return type for get(). If you pass in an improperly typed options object, it can't infer the right return type.

login(credentials: Credentials): Observable<any> {
    return this.httpClient.post<any>(`${environment.USER_SERVICE_BASE_URL}`,
      {'username': credentials.username, 'password': credentials.password}, {
      headers: new HttpHeaders({'Content-Type': 'application/json'}),
      observe: 'response'
    })
      .map((res) => ...