CODEWITHSUNDEEP
javascriptangularrxjsobservableangular2-observables
Chris Halcrow
Chris Halcrow

Reputation: 31940

angular2 rxjs Observable - supplied parameters do not meet signature of call target

I've created the following component, following the Angular code example for constructing a new observable (https://angular.io/guide/observables#creating-observables).

I get an error on the line where I try to create the new Observable, as I've indicated in the code sample below. The error is 'supplied parameters do not meet signature of call target'

What have I missed?

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';

@Component({
  selector: 'app-constructed-observable',
  templateUrl: './constructed-observable.component.html',
  styleUrls: ['./constructed-observable.component.css']
})
export class ConstructedObservableComponent implements OnInit {

  constructor() { }

  // error on Observable below 'supplied parameters do not meet signature of call target'
  const sequence = new Observable(sequenceSubscriber);

  function sequenceSubscriber(observer) {
    observer.next(1);
    observer.next(2);
    observer.next(3);
    observer.complete();

    return {unsubscribe() {}};
  }

  ngOnInit() {

    this.sequence.subscribe({
      next(num) { console.log(num); },
      complete() { console.log('completed'); }
    });

  }

}

Upvotes: 0

Views: 99

Answers (1)

Yerkon
Yerkon

Reputation: 4788

sequence is used in ngOnInit but not defined as class property.

Fix. component.ts:

 sequence: Observable<number>;

  constructor() {
    // error on Observable below 'supplied parameters do not meet signature of call target'
    this.sequence = new Observable(sequenceSubscriber);

    function sequenceSubscriber(observer) {
      observer.next(1);
      observer.next(2);
      observer.next(3);
      observer.complete();

      return { unsubscribe() { } };
    }
  }

StackBlitz Demo

Upvotes: 1

Related Questions