Updating Data with Scan

Would be worth mentioning you are using Rx.Js 5 Beta! It's not very clear and I spent a good while trying to figure out why switchMapTo wasn't working.

So essentially scan is equal to reduce, right? I don't understand why they always try to make another name in the world of RFP.

@Albert - no, reduce can only occur once a stream has completed. scan continues to gather output from streams over time and can continually update.

They to have the same api/usage, but the distinction is critical.

@john_lindquist you've made it abundantly clear that we shouldn't include business logic instead of a .subscribe() method.

So I'm creating a canActivate guard to protect against users going to an invalid route, and I can't help but build logic into the subscribe method. Is there a better way to do this?

import { Injectable } from '@angular/core';
import { CanActivate, ActivatedRouteSnapshot, Router } from '@angular/router';
import { Subscription } from 'rxjs/Subscription';
import { Subject } from 'rxjs/Subject';

import { Apollo, ApolloQueryObservable } from 'apollo-angular';

import { GQTicketId } from './ticket.model';



@Injectable()
export class TicketRouteActivatorService implements CanActivate {

  public ticket;
  private returnTrue: Subject<Boolean> = new Subject<Boolean>();
  private ticketSubscription: Subscription;

  constructor(private apollo: Apollo, 
              private router: Router) { }

  canActivate(route: ActivatedRouteSnapshot ) {

    this.ticketSubscription = this.apollo.watchQuery({
      query: GQTicketId,
      variables: {
        _id: +route.params['id']
      }
    }).subscribe(({data})=>{
      this.ticket = data['ticket'];

      // this doesn't seem right, atleast based on the guidance from John Linquidst. Should this logic be "Rx'd" some how?
      if(!this.ticket) {
          this.router.navigate(['provision/requests/error/404']);
      } else {
        this.returnTrue.next(true);
      }
        
    }
    );

      if (this.returnTrue) return true;
  }

  // do we need to unsubscribe?
  ngOnDestroy():void {
      this.ticketSubscription.unsubscribe();
  }

}

Wouldn't it be a bit simpler if we used the counter value instead of object?

.scan((acc) => ++acc, -1)