Angular Book

Manual Injection

You are not limited to automatic dependency injection mechanism. The Angular provides you with a low-level APIs that allow you to resolve and create instances manually from code.

The DI utility class is called ReflectiveInjector, and you can import it from the @angular/core namespace. It helps to create the injectors filled with resolved and created instances of the providers, similar to those we used with the application modules.

import { ReflectiveInjector } from '@angular/core';

@Component({/*...*/})
export class AppComponent {
  
  constructor() {
    const injector = ReflectiveInjector.resolveAndCreate([ LogService ]);
    const logService: LogService = injector.get(LogService);
    logService.info('hello world');
  }

}

Typically you are going to use this API only for concrete scenarios like unit testing or dynamic content creation.

You can get more detailed information including code examples in the following article: Reflective Injector.