未定义方法“ of”-Angular 5 HTTP服务教程

Question

I'am reading Angular 5 http tutorial . Everything worked fine, until I stuck on this weird construction wher my Ionic project is throwing error, that "of is not defined".

/**
* Handle Http operation that failed.
* Let the app continue.
* @param operation - name of the operation that failed
* @param result - optional value to return as the observable result
*/
private handleError<T> (operation = 'operation', result?: T) {
  return (error: any): Observable<T> => {

    // TODO: send the error to remote logging infrastructure
    console.error(error); // log to console instead

    // TODO: better job of transforming error for user consumption
    this.log(`${operation} failed: ${error.message}`);

    // Let the app keep running by returning an empty result.
    return of(result as T);
 };
}

I tired googling this "of" method, but with no success. Is this mistake in tutorial? Maybe some library?

Answer 1

of is a separate function. You need to import of function from rxjs package. RxJS 5.5 and later use this technique with separate functions. The most of functions you need to import, which lets you to have a clean code and also lets bundle tools to make some optimizations.

import { of } from 'rxjs/observable/of'

Answer 2

As shown in example you need to import that method:

import { of } from 'rxjs/observable/of';

See here in page: