Differences between Pipe and Tap when working with ngxsWhen working with

Question

Differences between Pipe and Tap when working with ngxsWhen working with

While experimenting with pipe and subscribe methods, I encountered an issue. When using pipe with tap, nothing gets logged in the console. However, when I switch to using subscribe, it works perfectly. Can you help me figure out what I'm doing wrong?

import { Observable } from 'rxjs';
import { tap, take } from 'rxjs/operators';

this.store.select(state => state.auth.authUser).pipe(
  take(1),
  tap((data) => {
    //Console output not working
    console.log('[Tap] User Data', data);

  })
);

this.store.select(state => state.auth.authUser).subscribe((data) => {
  // Console log displays user data
  console.log('[Subscribe] User Data', data);
})

I am currently utilizing RxJs version 6, TypeScript, and ngxs as my store in Angular 6.

angular rxjs pipe tap ngxs

Answer 1

Answer №1

There are two key aspects to consider in my response: your initial query and what you require 😉. Observable values only move through the pipe operators when there is an ongoing subscription, which explains the behavior you are observing. Therefore, the recommended approach is as follows:

this.store.select(state => state.auth.authUser).pipe(
  take(1),
  tap((data) => {
    console.log('[Tap] User Data', data)
  })
).subscribe();

However, if your goal is to obtain a snapshot of the state, you can achieve this by:

let data = this.store.selectSnapshot(state => state.auth.authUser);
console.log('[selectSnapshot] User Data', data);

Answer 2

There are two key aspects to consider in my response: your initial query and what you require 😉. Observable values only move through the pipe operators when there is an ongoing subscription, which explains the behavior you are observing. Therefore, the recommended approach is as follows:

this.store.select(state => state.auth.authUser).pipe(
  take(1),
  tap((data) => {
    console.log('[Tap] User Data', data)
  })
).subscribe();

However, if your goal is to obtain a snapshot of the state, you can achieve this by:

let data = this.store.selectSnapshot(state => state.auth.authUser);
console.log('[selectSnapshot] User Data', data);

Answer 3

Answer №2

tap (formerly known as do in earlier versions of RxJS) -> Performing actions or side-effects transparently, such as logging (as defined).

However, in this scenario, you neglected to "subscribe()" to your Observable, which is why you are not seeing the "User Data" in the Console.

Conversely, in the second scenario, you have already subscribed to an Observable.

Answer 4

tap (formerly known as do in earlier versions of RxJS) -> Performing actions or side-effects transparently, such as logging (as defined).

However, in this scenario, you neglected to "subscribe()" to your Observable, which is why you are not seeing the "User Data" in the Console.

Conversely, in the second scenario, you have already subscribed to an Observable.

Answer 5

Answer №3

Understood! I just need to add the subscribe() method like this:

this.store.select(state => state.auth.authUser).pipe(
  take(1),
  tap((data) => {
    console.log('[Tap] User Data', data)
  })
).subscribe();

Answer 6

Understood! I just need to add the subscribe() method like this:

this.store.select(state => state.auth.authUser).pipe(
  take(1),
  tap((data) => {
    console.log('[Tap] User Data', data)
  })
).subscribe();

Differences between Pipe and Tap when working with ngxsWhen working with

Answer №1

Answer №2

Answer №3

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