[Solved] Find the mistake in this Angular service using the Factory pattern:export... Find the mistake in this Angular service using the Factory pattern:export function createService() { return new Service(); | Angular

Angular - Advanced Patterns

Find the mistake in this Angular service using the Factory pattern:

export function createService() { return new Service(); }
@Injectable({ providedIn: 'root', useFactory: createService })
export class Service {}

AFactory function returns an instance of Service before Service is declared

BuseFactory should be a string, not a function

CService class cannot be injectable

DprovidedIn cannot be 'root' with useFactory

Step-by-Step Solution

Solution:

Step 1: Check order of declarations
The factory function createService returns new Service(), but Service class is declared after it, causing a reference error.
Step 2: Validate other options
useFactory should be a string, not a function is wrong because useFactory expects a function. Service class cannot be injectable is false; services can be injectable. providedIn cannot be 'root' with useFactory is incorrect; providedIn: 'root' works with useFactory.
Final Answer:
Factory function returns an instance of Service before Service is declared -> Option A
Quick Check:
Factory function must be declared after class or use forward references [OK]

Quick Trick: Factory function must not reference class before declaration [OK]

Common Mistakes:

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