ionViewDidLoad anf ngOnInit on child components

Ionic Framework ionic-v3
1

I have a page with Leaflet map on it which i initialize in ionViewDidLoad().Also I have a components that work with map, so i need to pass map instance through @Input().But when I try ngOnInit() or other angular’s strat-up hooks, the map is not initialized and I have ```undefined`` in my component.

P.s. ngOnChanges() is not an option.

2

For now i use Events that is not a good solution IMHO.

3

You’re giving the component data before the data is ready? Instead you could use an Observable and give the data when it is ready.

4

Thanks, Can you give an example?

5

Did you mean this aproach?

export class VehiclesForMapComponent implements OnInit {
  mapInitialized: boolean;
  private _map = new BehaviorSubject<L.Map>(null);
  @Input()
  set map(value) {
    this._map.next(value);
  };
  get map() {
    return this._map.getValue();
  }

  ngOnInit() {
    this.mapInitialized = false;
    this._map.filter(map => !!map).takeWhile(() =>  !this.mapInitialized).subscribe(map => {
      this.mapInitialized = true;
      ...
    });
  }
}
6

That’s inside the component. And I don’t understand the logic there – seems the filter should be inside the set, not the initialization. That way you don’t deal with pathological values of map at all. But I meant that the containing page should only send the component defined information. For example an Observable with a filter, and use the async pipe to pass info to the component.

7

One thing to note is that ngOnChanges() is the only place you can rely on @Input properties receiving their values. ngOnInit() = no good.

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