How to return as observer from localStorage or an other observer in Angular2?

Question

Here is my "loantype" service get() function:

get() {
  return new Observable(observer => {
    let response;
    if ( localStorage.getItem('loantypes_are_valid') === '1' ) {
      response = JSON.parse(localStorage.getItem('loantypes') || '[]');
    } else {
      response = this.getAll().subscribe(result => {
        localStorage.setItem('loantypes', JSON.stringify(result) );
        localStorage.setItem('loantypes_are_valid', '1');
      });
    }
    return response;
  });
}

I just want to use this service something like this:

this.loanTypes.get().subscribe(
  response => this.loantypes = response,
  (error: AppError) => {throw error; }
);

Now, the goal is to serve the datas from localStorage if it's valid, otherwise I need to reload it from the API server, store it into the localStorage (for the next requests) and serve the datas into the component.

This code store the datas into the localStorage, and after this happening something wrong and I can't figure out what is wrong. Any idea?

I get back an observable object, not a JSON object with the datas... — netdjw, Apr 18 '18 at 20:41
You want an Observable, right? And did you try adding a return under the Subscription? — Ashish Ranjan, Apr 18 '18 at 20:44
yes, but in the second part of my example code I want get a JSON object into the `this.loantypes` ... how can I do this? — netdjw, Apr 18 '18 at 20:45
The `response` under the second part will be a JSON object itself, because we are subscribing the Observable there. You don't get it as JSON? — Ashish Ranjan, Apr 18 '18 at 20:48
Can you do this? (response) => {console.log(response); this.loantypes = response} under the subscription? — Ashish Ranjan, Apr 18 '18 at 20:50
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/169279/discussion-between-netdjw-and-ashish-ranjan). — netdjw, Apr 18 '18 at 21:03

Ashish Ranjan · Accepted Answer · 2018-04-18T21:01:23.750

~~Try adding a return statement under subscription~~

localStorage.setItem('loantypes', JSON.stringify(result) );
localStorage.setItem('loantypes_are_valid', '1');
return result

Call the Observer's next()

 if () {
   observer.next(JSON.parse(...))
 }
 else {
    response = this.getAll().subscribe(result => {
       localStorage.setItem('loantypes', JSON.stringify(result) );
       localStorage.setItem('loantypes_are_valid', '1');
       observer.next(result) 
    });
 }
observer.complete()

How to return as observer from localStorage or an other observer in Angular2?

1 Answers1