1

I'm trying to fire an event when my component gets the logged user from a service because I would like to show the navigation bar only when a user is logged in.

Here's my app.component code:

import { Component, OnInit, EventEmitter, Input, Output } from '@angular/core';
import { ROUTER_DIRECTIVES, Router } from '@angular/router';
import { LoginComponent } from './login.component';
import { DashboardComponent } from './dashboard.component';
import { ControlDetailComponent } from './control-detail.component';
import { PageNotFoundComponent } from './pagenotfound.component';
import { SettingsComponent } from './settings.component';
import { UserService } from '../service/user.service';
import { User } from '../object/user';

@Component({
    selector: 'myApp',
    templateUrl: './app/template/app.component.html',
    styleUrls: ['styles.css'],
    directives: [ROUTER_DIRECTIVES],
    precompile: [LoginComponent, DashboardComponent, ControlDetailComponent, PageNotFoundComponent, SettingsComponent]
})
export class AppComponent {
    @Input() loggedUser:User;
    @Output() userChanged:EventEmitter<User> =  new EventEmitter<User>();

    constructor(private _userService:UserService, private _router:Router) {}

    ngAfterViewInit() { 
        if(this._userService.isUserLogged()) {
           this.userChanged.emit(this._userService.loggedUser);
       }
    }

    switchUser(event) {
        this.loggedUser = event.target.value;
        console.log("event triggered");
    }
}


And this is its associated template:

<div class="all-content">
<nav (userChanged)="switchUser($event)" *ngIf="loggedUser">
    <ul>
        <a [routerLink]="['/dashboard']" routerLinkActive="active">Dashboard</a>
        <a [routerLink]="['/settings']" routerLinkActive="active">Settings</a>
        <a (click)="logout()">Logout</a>
    </ul>
</nav>


Someone knows why my event is not fired?

Initially I thought the problem was the *ngIf directive that was preventing the firing of the event but, even removing that, the event is not fired anyway...

Andrea Caruso
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2 Answers2

3

Events emitted by @Output()s can only be subscribed to on the parent component or a directive applied on the element. The AppComponent doesn't have a parent component, therefore this approach won't work.

In your case it's better to use a shared service with observables. https://angular.io/docs/ts/latest/cookbook/component-communication.html

Günter Zöchbauer
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3

Solved using Observables and a Service, as Günter Zöchbauer suggested (thanks!).

Below my solution:

user.service.ts

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import { Observable } from 'rxjs/Rx';
import { Subject }    from 'rxjs/Subject';
import { Control } from '../object/control';
import { User } from '../object/user';


@Injectable()
export class UserService {
    private userChangedSource = new Subject<User>();
    userChanged = this.userChangedSource.asObservable();
    loggedUser:User;

    userLoggedIn(user:User) {
        this.loggedUser = user;
        this.userChangedSource.next(user);
    }

    ...
}

app.component.ts

import { Component, OnInit, EventEmitter, Input, Output } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { ROUTER_DIRECTIVES, Router } from '@angular/router';
import { LoginComponent } from './login.component';
import { DashboardComponent } from './dashboard.component';
import { ControlDetailComponent } from './control-detail.component';
import { PageNotFoundComponent } from './pagenotfound.component';
import { SettingsComponent } from './settings.component';
import { UserService } from '../service/user.service';
import { User } from '../object/user';

@Component({
    selector: 'myApp',
    templateUrl: './app/template/app.component.html',
    styleUrls: ['styles.css'],
    directives: [ROUTER_DIRECTIVES],
    precompile: [LoginComponent, DashboardComponent, ControlDetailComponent, PageNotFoundComponent, SettingsComponent]
})
export class AppComponent implements OnInit {
    loggedUser:User;

    constructor(private _userService:UserService, private _router:Router) { 
        this._userService.userChanged.subscribe(user => {
                this.loggedUser = user;
                console.log("event triggered");
        });
    }
    ...
}

app.component.html

<div class="all-content">
    <nav *ngIf="loggedUser" >
        <ul>
            <a [routerLink]="['/dashboard']" routerLinkActive="active">Dashboard</a>
            <a [routerLink]="['/settings']" routerLinkActive="active">Settings</a>
            <a (click)="logout()">Logout</a>
        </ul>
    </nav>
<router-outlet></router-outlet>
<br/>
</div>
Andrea Caruso
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  • 1
  • 9