Angular 7中的类型'OperatorFunction <{}，{}>'错误上不存在属性'subscribe'

Question

while learning how to handle errors in Angular Typescript threw an error

Property 'subscribe' does not exist on type 'OperatorFunction<{}, {}>' in this code block in my component

createPost(post: HTMLInputElement) {
this.service.newPost(post).subscribe(
  response => {
    this.posts.splice(0, 0, post);
  },
  (error: AppError) => {
    if (error instanceof BadInput) {
      // Set form errors and display them next to input fields
      this.form.setErrors(error.originalError);
    } else {
      alert("An unexpected error occurred.");
      console.log(error);
    }
  }
);
}

The service code returning the observable used by the component code is

newPost(post) {
return (
  this.http.post(this.url, post),
  catchError((error: Response) =>
    error.status === 400
      ? Observable.throw(new BadInput(error))
      : Observable.throw(new AppError(error))
  )
);
}

I need help resolving the error and an explanation on why the error is thrown or how best to achieve handling errors.

Answer 1

You should use pipe operator followed by a map operator followed by catchError operator. You will have to import the map operator and the catchError operator from rxjs/operators. Please see below:

.pipe(
    mergeMap(resp => {
        // add logic
    }),
    catchError(err => {
        // add handling 
    })
);