Why is my Angular signal effect not firing? - Stack Overflow

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The class below declares a signal and an update function for the signal:

export class ProductSidebarService {
  public productSidebarSignal = signal<{
    productSidebarData: ProductSidebarData;
  }>({ productSidebarData: new ProductSidebarData() });

  public updateSidebarData = (productSidebarData: ProductSidebarData) => {
    this.productSidebarSignal.set({productSidebarData:{... productSidebarData} });
    console.dir('ProductSidebarService.productSidebarSignal', this.productSidebarSignal())
  };
}

The class below declares an effect that is supposed to fire when the above signal is updated but the effect never fires:

export class ProductGalleryComponent {
  private productSidebarService = inject(ProductSidebarService);
  public productSidebarData = this.productSidebarService.productSidebarSignal();

  private productSidebarEffect = effect(() => {    
    console.dir('ProductGalleryComponent.productSidebarSignal', this.productSidebarService.productSidebarSignal())


  });
}

The class below declares a signal and an update function for the signal:

export class ProductSidebarService {
  public productSidebarSignal = signal<{
    productSidebarData: ProductSidebarData;
  }>({ productSidebarData: new ProductSidebarData() });

  public updateSidebarData = (productSidebarData: ProductSidebarData) => {
    this.productSidebarSignal.set({productSidebarData:{... productSidebarData} });
    console.dir('ProductSidebarService.productSidebarSignal', this.productSidebarSignal())
  };
}

The class below declares an effect that is supposed to fire when the above signal is updated but the effect never fires:

export class ProductGalleryComponent {
  private productSidebarService = inject(ProductSidebarService);
  public productSidebarData = this.productSidebarService.productSidebarSignal();

  private productSidebarEffect = effect(() => {    
    console.dir('ProductGalleryComponent.productSidebarSignal', this.productSidebarService.productSidebarSignal())


  });
}

• angular
• signals
• effect
• angular-signals

Share Improve this question Follow edited Nov 21, 2024 at 23:59 Naren Murali 54.6k55 gold badges4040 silver badges7070 bronze badges asked Nov 21, 2024 at 19:35 koquekoque 2,21666 gold badges3232 silver badges5353 bronze badges

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2 Answers 2

Sorted by: Reset to default 1

The problem might be console.dir, which does not show the output of the signal when passed in with comma separated values, apart from that from the data provided, the effect is firing.

Also make sure, you have console.log set on when you update the signal and when you initialize the effect, you can set a console.log on the constructor of ProductGalleryComponent if the component is initialized after the signal is set, the effect might fire only once.

Also note, that signal updates are kind of debounced, so it will fire only once.

import { Component, inject, Injectable, signal, effect } from '@angular/core';
import { bootstrapApplication } from '@angular/platform-browser';
import {
  HttpClient,
  HttpParams,
  provideHttpClient,
} from '@angular/common/http';
import { Observable, map } from 'rxjs';

export class ProductSidebarData {
  constructor(public test: string = '') {}
}
@Injectable({ providedIn: 'root' })
export class SomeService {
  public productSidebarSignal = signal<{
    productSidebarData: ProductSidebarData;
  }>({ productSidebarData: new ProductSidebarData() });

  public updateSidebarData = (productSidebarData: ProductSidebarData) => {
    this.productSidebarSignal.set({
      productSidebarData: { ...productSidebarData },
    });
    console.log(
      'ProductSidebarService.productSidebarSignal',
      this.productSidebarSignal()
    );
  };
}
@Component({
  selector: 'app-root',
  template: `asdf`,
})
export class App {
  productSidebarService = inject(SomeService);

  private productSidebarEffect = effect(() => {
    console.log(
      'ProductGalleryComponent.productSidebarSignal',
      this.productSidebarService.productSidebarSignal()
    );
  });
  constructor() {
    console.log('test');
  }

  ngOnInit() {
    console.log('storing');
    this.productSidebarService.updateSidebarData(
      new ProductSidebarData('qwerty')
    );
    this.productSidebarService.updateSidebarData(
      new ProductSidebarData('qwerty1')
    );
  }
}

bootstrapApplication(App, {
  providers: [provideHttpClient()],
});

Stackblitz Demo

Issues Effect Not Reacting: The effect in ProductGalleryComponent should directly reference the signal to react to changes. Initialization: Avoid capturing the initial state of the signal. the typescript code:-

import { effect, inject } from 'some-reactive-library'; // Adjust import based on your context

export class ProductGalleryComponent {
  private productSidebarService = inject(ProductSidebarService);

  constructor() {
    // Set up the effect to react to changes in the signal
    effect(() => {
      const currentSidebarData = this.productSidebarService.productSidebarSignal();
      console.dir('ProductGalleryComponent.productSidebarSignal', currentSidebarData);
    });
  }
}

whereas, the debug console:- Ensure 'updateSidebarData' is called with new data:

public updateSidebarData = (productSidebarData: ProductSidebarData) => {
  console.dir('Updating sidebar data', productSidebarData);
  this.productSidebarSignal.set({ productSidebarData: { ...productSidebarData } });
  console.dir('ProductSidebarService.productSidebarSignal', this.productSidebarSignal());
};

Hope embedding this changes its directly referencing the signal in the effect and ensuring updates change the state, the effect should fire correctly.

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