Question

我试图在ngrx效果中进行两个http调用。说我有要提取的评论。它首先拨打电话以获取最新评论，并检查它是否已出现在UI上；否则，我再次拨打电话并获取所有评论。这在连续轮询中运行。这是我的代码。我现在正在学习角度性和可观察性是一种混乱。

@Effect()
fetchAllComments: Observable<any> = this.actions$.pipe(
    ofType(commentsActions.FETCH_ALL_COMMENTS),
    withLatestFrom(this._store),
    mergeMap(([action, state]) => {
        return this._http.get(`${this.baseUrl}/comments/latest`)
            .pipe(
                catchError(error => {
                    console.log(error);
                    return this._error.handle(error, new commentsActions.FetchAllCommentsError)
                }))
            .subscribe(comment => {
                console.log("Response from server", comment);
                if (!!comment['id'] && state.comment.comments.every(n => n.id !== comment['id'])) {
                    console.log("making call to fetch api ");
                    return this._http.get(`${this.baseUrl}/comment`)
                        .pipe(
                            map((comments: any) => new commentsActions.FetchAllCommentsComplete(comments.message)),
                            catchError(error => {
                                return this._error.handle(error, new commentsActions.FetchAllCommentsError);
                            }));
                } else {
                    console.log("returning mock");
                    return of(state.comment.comments);
                }
            })
    }));

这是正确的方法吗？我从core.js:15724 ERROR TypeError: You provided an invalid object where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

开始遇到一堆错误

谢谢

Answer 1

您要从mergeMap返回订阅，您需要返回可观察对象，但是您已订阅它，而订阅就是您要返回的内容。

如何在ngrx效果中拨打两次电话

1 个答案: