Angular 8 References/ Core


This is the documentation for Angular 8.
You can switch to the latest version Angular 10.

A constructor parameter decorator that tells the DI framework to retrieve a dependency from any injector until reaching the host element of the current component.

constructor(@Host() service: Service) {}


class OtherService {}
class HostService {}

@Directive({selector: 'child-directive'})
class ChildDirective {
  logs: string[] = [];

  constructor(@Optional() @Host() os: OtherService, @Optional() @Host() hs: HostService) {
    // os is null: true
    this.logs.push(`os is null: ${os === null}`);
    // hs is an instance of HostService: true
    this.logs.push(`hs is an instance of HostService: ${hs instanceof HostService}`);

  selector: 'parent-cmp',
  viewProviders: [HostService],
  template: '<child-directive></child-directive>',
class ParentCmp {

  selector: 'app',
  viewProviders: [OtherService],
  template: '<parent-cmp></parent-cmp>',
class App {