You want to share user login status across multiple components using a singleton service. Which approach correctly ensures the service is singleton and updates are reflected everywhere?

hard🚀 Application Q15 of 15

Angular - Services and Dependency Injection

ACreate service with <code>@Injectable({ providedIn: 'root' })</code> and use a BehaviorSubject to hold login status.

BCreate service without providedIn and add it to each component's providers array.

Create service with <code>@Injectable({ providedIn: 'root' })</code> but store login status in a local variable inside each component.

DCreate service with <code>@Injectable()</code> and manually instantiate it in each component constructor.

Step-by-Step Solution

Solution:

Step 1: Ensure singleton service provision
Using providedIn: 'root' makes the service singleton app-wide.
Step 2: Use BehaviorSubject for reactive shared state
BehaviorSubject allows components to subscribe and get updates when login status changes.
Step 3: Evaluate other options
Options B, C, and D break singleton or do not share state properly.
Final Answer:
Create service with @Injectable({ providedIn: 'root' }) and use a BehaviorSubject to hold login status. -> Option A
Quick Check:
Singleton + reactive state = shared updates [OK]

Quick Trick: Use providedIn: 'root' and BehaviorSubject for shared reactive state [OK]

Common Mistakes:

MISTAKES

Adding service to component providers breaking singleton
Storing shared data only inside components
Manually creating service instances instead of DI

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More Angular Quizzes

You want to share user login status across multiple components using a singleton service. Which approach correctly ensures the service is singleton and updates are reflected everywhere?

Step 1: Ensure singleton service provision

Step 2: Use BehaviorSubject for reactive shared state

Step 3: Evaluate other options

Final Answer:

Quick Check:

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