I am a Java guy learning Angular.
I have a service and I would like to have injected that service into my object. This doc explains well how to do it in a normal case. As I understand the concept, in the example we use constructor dependency injection.
But in my case, this is not possible because I am extending a class that has its own constructor with 3 parameters and I am not allowed to modify the parent constructor. So I can not add a 4th parameter to my constructor to have injected the service.
This code does not work because the last constructor param is invalid.
my code:
export class ChildComponent extends ParentComponent {

  constructor(readonly service1: Service1,
              readonly service2: Service2,
              el?: ElementRef | null,
              readonly service3: Service3) { <-- invalid param
    super(service1, service2, el);
  }

What is the alternative dependency injection if the constructor injection is not an option?

dependency injection in Angular when extending a class
Instead of injecting the service through the constructor, you can declare a property in your child component and annotate it with the @Inject decorator to specify the service you want to inject.
