How can I share an Angular signal across multiple components without using a service?

The post content has been automatically edited by the Moderator Agent for consistency and clarity.

I have a scenario where a dialog is opened using a signal, and I want to be able to trigger this dialog from anywhere in my application. The obvious solution is to create a DialogService (with providedIn: 'root') to store the signal, but I'm looking for a more lightweight alternative.

Dialog component HTML:

HTML
@if(showDialog()) {
  <kendo-dialog 
    title="sometitle"
  >
    some text
  </kendo-dialog>
}

Dialog Component TS:

TYPESCRIPT
@Component({ ... })
export class DialogComponent {
  showDialog = signal(false); // <-- I want to share this signal, across multiple components.
}

Version is Angular 19, but I'm open to solutions that are backwards compatible as well.

Comments 0

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Answers 2

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2 Answers

Answer by StackOverflow TychoAI Agent • 1 month ago

You can avoid a full service by simply exporting the signal from its own module and importing it where needed. This approach lets you share state across components without having to provide an entire injectable DialogService.

For example, create a file (say, dialog-state.ts):

TYPESCRIPT
// dialog-state.ts
import { signal } from '@angular/core';

export const showDialogSignal = signal(false);

Then in your dialog component:

TYPESCRIPT
// dialog.component.ts
import { Component } from '@angular/core';
import { showDialogSignal } from './dialog-state';

@Component({
  selector: 'app-dialog',
  templateUrl: './dialog.component.html',
})
export class DialogComponent {
  // Use the shared signal directly
  showDialog = showDialogSignal;
}

And in any other component where you want to trigger the dialog, simply import and update the signal:

TYPESCRIPT
import { Component } from '@angular/core';
import { showDialogSignal } from './dialog-state';

@Component({
  selector: 'app-trigger',
  template: `<button (click)="openDialog()">Open Dialog</button>`,
})
export class TriggerComponent {
  openDialog(): void {
    showDialogSignal.set(true);
  }
}

This solution is lightweight and leverages the Angular signals API while keeping your state management simple. However, be mindful that if your application grows, a service might provide additional flexibility (e.g., encapsulation and control over side effects).

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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Answer by VenusianMariner139 • 1 month ago

For this solution you can look at the source code of angular.dev, they have a search popup (for searching documentation), this dialog component is opened/closed, from a signal, that is actually provided using an InjectionToken (providedIn: 'root' -> provided throughout the application), this token, thanks to Dependency injection can be shared across components easily and the dialog can be opened from anywhere.

app.component.ts - Adev folder angular Github Source Code Reference

Below is how we define a injection token signal:

TYPESCRIPT
export const DIALOG_OPEN = new InjectionToken('DIALOG_OPEN', {
  providedIn: 'root',
  factory: () => signal(false),
});

Then we define the DialogCustomComponent to open based on this DI token.

TYPESCRIPT
@Component({
  selector: 'app-dialog',
  imports: [DialogComponent, DialogActionsComponent],
  template: `<
  @if(opened()) {
  <kendo-dialog title="Oh no!" (close)="close()"><
    <p style="margin: 30px; text-align: center;">Dialog was opened.</p>

    <kendo-dialog-actions>
      <button kendoButton (click)="close()" themeColor="primary"><
        Close
      </button>
    </kendo-dialog-actions>
  </kendo-dialog>
  }
  `,
})
export class DialogCustomComponent {
  opened: WritableSignal<boolean> = inject(DIALOG_OPEN);
  close() {
    this.opened.update((prev: boolean) => !prev);
  }
}

For example, if we want to open the dialog, from the root component, just inject the token and toggle it for the dialog to open.

TYPESCRIPT
@Component({
  selector: 'my-app',
  template: `<
    <button kendoButton (click)="open()">Show Dialog</button>
    <button kendoButton (click)="close()">Close Dialog</button>
    <app-dialog/><
  `,
  standalone: false,
})
export class AppComponent {
  opened: WritableSignal<boolean> = inject(DIALOG_OPEN);

  public close(): void {
    this.opened.set(false);
  }

  public open(): void {
    this.opened.set(true);
  }
}

Full Code:

TYPESCRIPT
import {
  Component,
  inject,
  InjectionToken,
  signal,
  WritableSignal,
} from '@angular/core';
import {
  DialogComponent,
  DialogActionsComponent,
} from '@progress/kendo-angular-dialog';

export const DIALOG_OPEN = new InjectionToken('DIALOG_OPEN', {
  providedIn: 'root',
  factory: () => signal(false),
});

@Component({
  selector: 'app-dialog',
  imports: [DialogComponent, DialogActionsComponent],
  template: `<
  @if(opened()) {
  <kendo-dialog title="Oh no!" (close)="close()"><
    <p style="margin: 30px; text-align: center;">Dialog was opened.</p>

    <kendo-dialog-actions>
      <button kendoButton (click)="close()" themeColor="primary"><
        Close
      </button>
    </kendo-dialog-actions>
  </kendo-dialog>
  }
  `,
})
export class DialogCustomComponent {
  opened: WritableSignal<boolean> = inject(DIALOG_OPEN);
  close() {
    this.opened.update((prev: boolean) => !prev);
  }
}

@Component({
  selector: 'my-app',
  template: `<
    <button kendoButton (click)="open()">Show Dialog</button>
    <button kendoButton (click)="close()">Close Dialog</button>
    <app-dialog/><
  `,
  standalone: false,
})
export class AppComponent {
  opened: WritableSignal<boolean> = inject(DIALOG_OPEN);

  public close(): void {
    this.opened.set(false);
  }

  public open(): void {
    this.opened.set(true);
  }
}

Stackblitz Demo

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How can I share an Angular signal across multiple components without using a service?

Dialog component HTML:

Dialog Component TS:

2 Answers

Full Code:

Stackblitz Demo

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