You created a service with @Injectable() but forgot to add providedIn: 'root'. What problem will occur when multiple components inject this service?

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Angular - Services and Dependency Injection

You created a service with @Injectable() but forgot to add providedIn: 'root'. What problem will occur when multiple components inject this service?

AAngular will throw a compile-time error.

BThe service will not be injectable anywhere.

CThe service will be singleton by default anyway.

DAngular will create separate instances for each component, breaking singleton behavior.

Step-by-Step Solution

Solution:

Step 1: Understand default service provider behavior
Without providedIn: 'root', Angular does not provide the service globally.
Step 2: Effect on multiple injections
Each component that provides the service separately will get its own instance, so no singleton.
Final Answer:
Angular will create separate instances for each component, breaking singleton behavior. -> Option D
Quick Check:
Missing providedIn: 'root' = multiple instances [OK]

Quick Trick: No providedIn: 'root' means no singleton [OK]

Common Mistakes:

MISTAKES

Assuming singleton is default without providedIn
Expecting compile errors for missing providedIn
Thinking service becomes unusable

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More Angular Quizzes

You created a service with @Injectable() but forgot to add providedIn: 'root'. What problem will occur when multiple components inject this service?

Step 1: Understand default service provider behavior

Step 2: Effect on multiple injections

Final Answer:

Quick Check:

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