[Solved] Which of the following is the correct syntax to inject AuthService into UserService constructor? - Ans: constructor(private authService: AuthService) {} | Angular

Angular - Services and Dependency Injection

Which of the following is the correct syntax to inject AuthService into UserService constructor?

Aconstructor(@Inject AuthService authService) {}

Bconstructor(private authService: AuthService) {}

Cconstructor(authService = new AuthService()) {}

Dconstructor(AuthService authService) {}

Step-by-Step Solution

Solution:

Step 1: Recall Angular constructor injection syntax
Angular uses TypeScript constructor parameters with access modifiers to inject services.
Step 2: Evaluate options
constructor(private authService: AuthService) {} uses correct syntax with private modifier and type. constructor(AuthService authService) {} misses access modifier, C manually creates instance (not injection), A uses incorrect decorator syntax.
Final Answer:
constructor(private authService: AuthService) {} -> Option B
Quick Check:
Constructor injection syntax = private param with type [OK]

Quick Trick: Use private/public in constructor for injection [OK]

Common Mistakes:

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Which of the following is the correct syntax to inject AuthService into UserService constructor?