My favorite way to do is by using behavior subject or event emitter (almost the same) in my service to control all my subcomponent.
Using angular cli, run ng g s to create a new service then use a BehaviorSubject or EventEmitter
export Class myService {
#all the stuff that must exist
myString: string[] = [];
contactChange : BehaviorSubject<string[]> = new BehaviorSubject(this.myString);
getContacts(newContacts) {
// get your data from a webservices & when you done simply next the value
this.contactChange.next(newContacts);
}
}
When you do that every component using your service as a provider will be aware of the change. Simply subscribe to the result like you do with eventEmitter ;)
export Class myComp {
#all the stuff that exists like @Component + constructor using (private myService: myService)
this.myService.contactChange.subscribe((contacts) => {
this.contactList += contacts; //run everytime next is called
}
}