Suppose you have a parent component A and inside of it you have some variable x. You would like to pass this variable to the child component B. Easy! Just use @Input annotation and call it a day. But what if B has another child component C? How would we pass x from A to C? I tried using the same approach to pass it from B to C, but it only passes the value undefined.
>Solution :
You can use a common service file which is data.service.ts file in this case. This service will be injected by both the parent and grand child. When component A which is grand parent here want to send a data it will call the deliverMsg method of the data service file. The component C which is grand child will listen to this change by injecting the same data.service
data.service.ts
// relevant imports
@Injectable()
export class DataService {
private message = new BehaviorSubject('default message');
portMessage = this.message.asObservable();
constructor() { }
deliverMsg(message: string) {
this.message.next(message)
}
}
parent.component.ts
//all relevant imports
@Component({
selector: 'app-parent-a',
template: 'html file url',
styleUrls: ['./sibling.component.css']
})
export class ParentComponent implements OnInit {
message:string;
constructor(private data: DataService) { }
ngOnInit() {
}
newMessage() {
this.data.deliverMsg("Hello from Grand Parent")
}
}
grandchild.component.ts
// all relevant imports
@Component({
selector: 'app-sibling',
template: 'template',
styleUrls: ['./sibling.component.css']
})
export class SiblingComponent implements OnInit {
message:string;
constructor(private data: DataService) { }
ngOnInit() {
this.data.portMessage.subscribe(message => this.message = message)
}
}