I am working with classes parent and child. The child class is an extension of the parent class. I want to inject the injectable class service into the parent class since all instances of the child class will be using it as well. Can someone guide me on how to achieve this?
To access any service or class from the parent component, you can utilize the Injector class. By injecting the Injector class in the child component and passing it to the parent using super(injector), the parent component can then inject reusable services from the child's injector.
Example of Parent Component :
export class BaseComponent implements OnInit {
protected myService: MyService;
constructor(injector: Injector) {
this.myService = injector.get(MyService);
}
ngOnInit() {
console.log('ngOnInit from Base');
}
}
Example of Child Component :
export class AppComponent extends BaseComponent {
constructor(injector: Injector) {
super(injector);
}
ngOnInit() {
super.ngOnInit();
this.myService.getUsers();
}
}
This approach eliminates the need to individually inject each service from the child component to the parent component. Instead, it provides a more efficient way to inject services from the parent component.
Angular doesn't automatically instantiate a parent class, so you can't inject a dependency into it directly. The workaround is to make the child classes injectable and pass the dependencies up using super.
class Parent {
constructor(protected someService: SomeService) { }
}
@Injectable()
class Child extends Parent {
constructor(someService: SomeService) {
super(someService);
}
}
If the parent class doesn't require the dependency itself, it's recommended to mark the child classes as @Injectable() instead, allowing them to have their own private reference to the dependency.
To prevent the need to continuously pass either the injector or the injected instance from the child class to the parent class, consider utilizing the following alternative approach.
Start by creating a class with a single static property:
export class AppServices {
static injector: Injector;
}
Next, assign a value to the injector within the module where your service is initialized:
import {Injector, NgModule} from '@angular/core';
@NgModule({
providers: MyService
})
export class AppModule {
constructor(private injector: Injector) {
AppServices.injector = this.injector;
}
}
Once the module has been instantiated, you can utilize the static injector in any class to access any of the module's services:
export class ParentComponent {
private myService: MyService;
constructor () {
this.myService = AppServices.get<MyService>(MyService);
}
}
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