How do you diagnose an injector fault

Question

Explain me with the help of an example How do you diagnose an injector fault?

Answer 1

To diagnose an injector fault in Angular, follow these precise steps:

1. Check for Missing Provider

Error: NullInjectorError: No provider for <Service>!

Solution: Ensure the service is provided in the module or component using providers or @Injectable({ providedIn: 'root' }).

2. Check for Circular Dependencies

Error: Cannot instantiate cyclic dependency!

Solution: Refactor code to remove circular dependencies or use Injector for lazy injection.

3. Verify Injection Tokens

Error: StaticInjectorError: No provider for <Token>!

Solution: Ensure the token is correctly provided and injected using @Inject.

4. Check Lazy-Loaded Modules

Error: NullInjectorError: No provider for <Service>!

Solution: Provide the service in the root injector or ensure it’s available in the lazy-loaded module.

5. Add @Injectable Decorator

Error: Can't resolve all parameters for <Service>!

Solution: Add the @Injectable decorator to the service.