Using shareReplay(1) in Angular - still invokes http request?

Question

I\'ve created a demo (ng-run) where I have a button which invokes an Http request.

When the button is clicked, I invoke this method :

public getData         


        

Answer 1

If you call every time this.http.get(API_ENDPOINT).pipe(shareReplay(1)), each time http request will be triggered. If you want to make http call once and cache data, the following is recommended.

You first get the observable for data:

 ngOninit(){
    this.data$ =  this._jokeService.getData().pipe(shareReplay(1));
    }

Now subscribe multiple times:

 public getData(){
     this.data$.subscribe();
    }

Your service:

public getData() {
    return this.http.get(API_ENDPOINT)
  }

Answer 2

In service:

getData$ = this.http.get(API_ENDPOINT).pipe(shareReplay(1));

In component, need to unsubscribe and you can subscribe multiple times with single API call:

ngOninit(){
   this.data$ =  this._jokeService.getData$;
   this.data$.subscribe() 
}

In template, use:

*ngIf="data$ | async as data"