What is the method for retrieving information from the store in an ngrx effect?

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The method for retrieving information from the store in an ngrx effect is by using the select operator from the @ngrx/store package. Here's an example:

import { Injectable } from '@angular/core';
import { Actions, createEffect, ofType } from '@ngrx/effects';
import { select, Store } from '@ngrx/store';
import { map, mergeMap } from 'rxjs/operators';
import { AppState } from '../app.state';
import { LoadUserAction, LoadUserSuccessAction, UserActionTypes } from './user.actions';
import { UserService } from './user.service';

@Injectable()
export class UserEffects {
  loadUser$ = createEffect(() =>
    this.actions$.pipe(
      ofType<LoadUserAction>(UserActionTypes.LOAD_USER),
      mergeMap(action => 
        this.store.pipe(
          select(state => state.auth.token),
          mergeMap(token => this.userService.getUser(action.payload.id, token)),
          map(user => new LoadUserSuccessAction(user))
        )
      )
    )
  );

  constructor(
    private actions$: Actions,
    private store: Store<AppState>,
    private userService: UserService
  ) {}
}

In this example, we're using the select operator to extract the token from the store, which we need to pass along with the user ID to the getUser method on the UserService. The result of that method call is then mapped to a new LoadUserSuccessAction that gets dispatched back to the store.