[Solved] Consider this facade service snippet:export class UserFacade { constructor(private userService:... } }What happens if userService is not provided in any module? | Angular

Angular - Advanced Patterns

Consider this facade service snippet:

export class UserFacade {
  constructor(private userService: UserService) {}
  getUser() { return this.userService.getUserData(); }
}

What happens if userService is not provided in any module?

AThe facade service creates a new instance automatically.

BThe facade service works but returns undefined.

CAngular throws a runtime error about missing provider.

DAngular silently ignores the missing service.

Step-by-Step Solution

Solution:

Step 1: Understand Angular dependency injection
Services must be provided to be injected; otherwise Angular errors at runtime.
Step 2: Identify behavior when provider is missing
Missing provider causes Angular to throw an error about no provider found.
Final Answer:
Angular throws a runtime error about missing provider. -> Option C
Quick Check:
Missing provider = runtime error [OK]

Quick Trick: Always provide services to avoid injection errors [OK]

Common Mistakes:

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