CODEWITHSUNDEEP
angularrxjsngrxngrx-effects
Lester Gray
Lester Gray

Reputation: 337

How to handle an If-else condition in an Effect to either throw an error or return a response from an API?

I am trying to check for a condition based on which I will either throw an error or continue down to calling an API which shd return a response. I'm not sure how to approach this.

Not very good in rxjs. newbie learning the ropes. Would the following code achieve this? ie in case I dont have a pizza id I would like to fire another error effect else call an API to get the pizzas

getPizzas$ = this.actions$.pipe(
  ofType<GetAllPizzas>(PizzaTypes.GetPizzas,
  withLatestFrom(
    this.store$.pipe(select(fromRootStore.getPizzaId))
  ),
  take(1),
  exhaustMap(([customAction, pizzaId]): any => {  // << assuming this is correct
    if (!pizzaId) {                       
      map(() => new BigProductError({ .   /// <<< is this how we approach this? just map? or should we return something?
           appmessage : "Boom"
      }));
    } .      /// <<< will control go beyond this point or is this more of an if-else condition?
    return this.pizzaService.getPizzas(customAction.orderDetails, pizzaId)
      .pipe(
        map((pizzas) => new LoadPizzasSuccess(pizzas)),
        catchError(error => of(new LoadPizzasFailure(error)))
      );
  })
);```

Upvotes: 1

Views: 1152

Answers (1)

Reactgular
Reactgular

Reputation: 54811

You should throw the BigProductError error so that subscribers can catch it using catchError(). Since it is thrown there is no else block required for the if statement.

getPizzas$ = this.actions$.pipe(
  ofType<GetAllPizzas>(PizzaTypes.GetPizzas),
  withLatestFrom(this.store$.pipe(select(fromRootStore.getPizzaId))),
  take(1),
  mergeMap(([customAction, pizzaId]) => {
    if (!pizzaId) {                       
      throw new BigProductError({appmessage : "Boom"}));
    }
    return this.pizzaService.getPizzas(customAction.orderDetails, pizzaId)
      .pipe(
        map((pizzas) => new LoadPizzasSuccess(pizzas)),
        catchError(error => of(new LoadPizzasFailure(error)))
      );
  })
);

I would also use mergeMap() after the take(1) because there will only be one value emitted.

Upvotes: 1

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