How to wait for user click event in angular2?

Question

So I have two components in Angular2. When a user clicks a button in component1, I have a method that stores a data in the sharedservice to a variable. This variable is accessed in component2 ngOnInit() . However the variable in initialised to undefined in ngOnInit() because it doesn't wait for the click event.

All In all, how can I have angular2 component2 wait for click event in component1?

In JavaScript, we can easily do this using click event listener or have a callback function, but I don't know how to implement the same idea in angular.

Could you please share your ideas.

This is what I have so far:

modules.component.html

<tr *ngFor="let module of modules" #moduleObject>
  <a class="test" (click)="module._clicked = !module._clicked"></a>
  <ul class="dropdown-menu" role="menu" [ngStyle]="{'display': module._clicked ? 'block' : 'none'}" >
    <li><a (click)="_showDialogue =! _showDialogue; _getModuleCode(module)"><img src="../../assets/img/pencil.svg" alt="" width="13px">Edit Module</a></li>

  </ul>
</tr>

I'll remove unecessary code from modules.component.ts as it will just blow everything in here modules.component.ts

import {SharedService} from "../shared/shared.service";
import {DepartmentsService} from "./departments.service";
import {ActivatedRoute, Params} from "@angular/router";
import {Module} from "../dashboard/Module";

@Component({
  selector: 'app-modules',
  templateUrl: './modules.component.html',
  providers: [DepartmentsService]
})
export class ModulesComponent implements OnInit {
  service;

  modules: Module[];

  constructor(
    private activatedRoute: ActivatedRoute,
    service : SharedService,
    private departmentsService: DepartmentsService,
    route: ActivatedRoute) {
    route.params.subscribe(p => {this.department = p['dname']; });
    this.service = service;
  }

  _getModuleCode(moduleObject) {
    this.departmentsService.moduleObject = moduleObject;
  }


  ngOnInit() { }
}

departments.service.ts

// assume necessary imports above
@Injectable()
export class DepartmentsService {
  public _facultyName     :string;
  public _departmentName  :string;
  public moduleObject:Module;
  constructor() {}
}

Then I call the moduleObject variable from this component: edit-forms.component.html

import {Module} from "./Module";
import {DepartmentsService} from "../components/departments.service";
//Change
@Component({
  selector: 'enable-module-form',
  templateUrl: './edit-forms.component.html',
  providers:[ModuleService]
})
export class EnableModFormComponent {
  constructor( 
    private moduleService: ModuleService, 
    private departmentService: DepartmentsService 
  ) { }

  ngOnInit(){
    console.log(this.departmentService.moduleObject);
  }

}

Answer 1

This should work!

DepartmentService:

private moduleSource = new Subject<any>();
moduleValue = this.moduleSource.asObservable();

moduleValueReceived(module) {
  //emit value
  this.moduleSource.next(module)
}

and in your parent, when you have the value set the value in the service:

_getModuleCode(moduleObject) {
   this.departmentsService.moduleValueReceived(moduleObject);
}

and in your child constructor, subscribe to the value:

constructor( 
  private moduleService: ModuleService, 
  private departmentService: DepartmentsService 
) { 
     moduleService.moduleValue.subscribe(moduleObject => {
        console.log(moduleObject); // here you have your value
     })
  }

Here in the official docs you have the equivalent example with further explanations than I have provided.

Hope this helps!