Update your get_categories() method to return the total (wrapped in an observable):
// Note that .subscribe() is gone and I've added a return.
get_categories(number) {
return this.http.post( url, body, {headers: headers, withCredentials:true})
.map(response => response.json());
}
In search_categories(), you can subscribe the observable returned by get_categories() (or you could keep transforming it by chaining more RxJS operators):
// send_categories() is now called after get_categories().
search_categories() {
this.get_categories(1)
// The .subscribe() method accepts 3 callbacks
.subscribe(
// The 1st callback handles the data emitted by the observable.
// In your case, it's the JSON data extracted from the response.
// That's where you'll find your total property.
(jsonData) => {
this.send_categories(jsonData.total);
},
// The 2nd callback handles errors.
(err) => console.error(err),
// The 3rd callback handles the "complete" event.
() => console.log("observable complete")
);
}
Note that you only subscribe ONCE, at the end.
Like I said in the comments, the .subscribe() method of any observable accepts 3 callbacks like this:
obs.subscribe(
nextCallback,
errorCallback,
completeCallback
);
They must be passed in this order. You don't have to pass all three. Many times only the nextCallback is implemented:
obs.subscribe(nextCallback);