Wait for http inside Guard on Angular 5

Question

I'm using a Guard on an Angular application to resolve initial critical data. On the version 4 of Angular I was duing it like this:

// app.routing.ts
routing = [{
    path: '', component: AppComponent, canActivate: [ResolveGuard],
}];

// resolve.guard.ts
@Injectable()
export class ResolveGuard implements CanActivate {
    constructor(
        private _api: ApiService,
    ) { }

    canActivate(): any {
        return this._api.apiGet('my/url').map(response) => {
            if ( response.status === 'success') {
                // Consume data here
                return true;
            }

            return false;
        }).first();
    }
}

Since the new version of Http on Angular 5 doesn't use the .map() property anymore, this is not working.

If I change .map() to .subscribe() it doesn't throw any errors, but the application never resolve properly. On the other hand, using .first() and/or .map() throw some errors, as expected in this version.

What should I do in this case?

I need to activate that route only if and when the initial data is loaded.

---

Edit to add info about the apiGet function:

constructor(private _http: HttpClient) {}

public apiGet(url: string): any {
    return this._http
        .get(this.apiUrl + url)
        .catch(this.handleError.bind(this));
}

Answer 1

So, first thing first: avoid the use of any when possible, specially when you know which type belongs where.

export interface FooInterface {
  status: string;
  fooString : string;
  fooNumber : number;
}

First Ill define the interface of the service in a clean manner, and then Ill refactor the guard class.

UPDATED ANSWER for rxjs 6.x

import { throwError, Observable } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable()
export class FooService {
   constructor(private _http: HttpClient) {}

   public apiGet(url: string): Observable<FooInterface> {
    return this._http
        .get<FooInterface>(this.apiUrl + url)
        .pipe(
          catchError(error => {
             // do general error handling if necessary and throw
            throwError(error);
           })
        );
  }
}

The guard class:

import { of, Observable } from 'rxjs';
import { map, catchError } from 'rxjs/operators';

@Injectable()
export class ResolveGuard implements CanActivate {
constructor(
    private fooService: FooService ,
) { }

canActivate(): Observable<boolean> {
    return this.fooService.apiGet('my/url')
       .pipe(
         map(response => response.status === 'success'),
         catchError(error => of(false))
       );
}

ORIGINAL ANSWER for rxjs 5.x

import { _throw } from 'rxjs/observable/throw':

constructor(private _http: HttpClient) {}

public apiGet(url: string): Observable<FooInterface> {
    return this._http
        .get<FooInterface>(this.apiUrl + url)
        .catch(error => {
          // do general error handling if necessary and throw
          _throw(error);
       });
}

The guard class:

import { of } from 'rxjs/observable/of';

@Injectable()
export class ResolveGuard implements CanActivate {
constructor(
    private _api: ApiService,
) { }

canActivate(): Observable<boolean> {
    return this._api.apiGet('my/url')
       .map(response => {
          let val = false;
          if ( response.status === 'success') {
                // Consume data here
                val = true;
          }
          return val;
        }).catch(error => {
          // consume the error maybe?
          of(false)
        });
}