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What is the difference between providing a service in root vs in a component?

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01

Understand the problem

Explain provider scope.

diprovidedin
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03

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providedIn: 'root' (or providing at the app level) creates one singleton shared everywhere. Providing a service in a component's providers array creates a new instance per component instance (and its children) — useful for component-scoped state that shouldn't be shared.

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04

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Root singleton vs component-scoped
import { Component, Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })   // ONE shared instance app-wide
export class GlobalCart {}

@Injectable()                          // not auto-provided
export class WidgetState {}

@Component({
  selector: 'app-widget',
  standalone: true,
  providers: [WidgetState],            // NEW WidgetState per <app-widget>
  template: '...',
})
export class WidgetComponent {
  // each <app-widget> gets its own WidgetState;
  // GlobalCart is the same instance everywhere.
}
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