Angular 2 ngOnInit is not called when routerlink changes

Question

i have a menu bar that contain a list of menus loaded from express api and every menu is referenced to a page that have an alias wich will be the URL of that page i am trying to load the page when i click to menu, it's done but only when i refresh the page this my menu code

export class MenuList implements OnInit {

menus:Menu[];
menu:Menu;
page:Page;

constructor(private router:Router,
            private menuService:MenuService) {
}

getMenus():void {
    this.menuService.getMenus()
        .subscribe(
            menus => this.menus = menus, //Bind to view
            err => {
                // Log errors if any
                console.log(err);
            }
        );
}

getPage(id):void {
    this.menuService.getPage(id)
        .subscribe(
            page => this.page = page, //Bind to view
            err => {
                // Log errors if any
                console.log(err);
            });
}

ngOnInit():void {
    this.getMenus();
}

}

and this is my template menu

<div class="container-fluid">
    <!-- Brand and toggle get grouped for better mobile display -->
    <div class="navbar-header">
        <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false">
            <span class="sr-only">Toggle navigation</span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
        </button>
    </div>

    <!-- Collect the nav links, forms, and other content for toggling -->
    <div class="collapse navbar-collapse" id="navbar"  style="background-color: #97455f">
        <div class="navv">
            <ul *ngFor="let menu of menus">
                <li class="col-lg-1 col-md-1 col-xs-12 col-sm-12"><a [routerLink]="[menu.page.alias]">{{menu.title}}</a></li>


            </ul>
        </div>
    </div>

</div><!-- /.navbar-collapse -->

I think the problem is in the ngOnInit of my page component, it's not called

    @Component({
    selector: 'page',
    templateUrl: './page.component.html'
})
export class PageComponent implements OnInit {
    alias: string;
    page:Page;

    constructor(private router:Router,
                private route: ActivatedRoute,
                private pageService:PageService) {

        this.route.params.subscribe(
            (params : Params) => {
                this.alias = params["alias"];
                console.log(this.alias)
            }
        );
    }




    ngOnInit():void {
        debugger;
        this.pageService.getPage(this.alias).subscribe(page => {
            this.page = page;
            console.log(this.page);
        });
    }

}

and this is my page template

    <p *ngIf="page" [innerHTML]="page.content" ></p>

this is my app routing code

const routes: Routes = [
    { path: '', redirectTo: '/home', pathMatch: 'full' },
    { path: ':alias', component: PageComponent },
    { path: 'archived',  component: ArchivedComponent },
    { path: 'home',  component: HomeComponent },
    { path: 'menu',  component: MenuList },
    { path: 'detail/:id', component: ActualiteDetailComponent },
    { path: 'contact',  component: ContactComponent },

];

@NgModule({
    imports: [ RouterModule.forRoot(routes) ],
    exports: [ RouterModule ]
})
export class AppRoutingModule {}

this is my app component

@Component({
  selector: 'my-app',
  template: `
    <menu-list></menu-list>
    <hr>
`

})
export class AppComponent {

}

Home of application with the menu bar

Answer 1

Here is a code example of what Gunter is talking about:

  constructor(private route: ActivatedRoute) { }

  ngOnInit() {
     this.route.params.subscribe(
     params => {
        let id= +params['id'];
        this.getProduct(id);
     });
  }

This code watches for changes to the parameters and executes any code inside the arrow function.

Answer 2

When only a router parameter is changes but the base of the route stays the same, Angular reuses the component. ngOnInit() is only called once after a component is instantiated, but not when the route changes.

You can inject the router and subscribe to it's events or params to get notified about route changes.

Answer 3

Well it fixed thanks to @Günter Zöchbauer and @DeborahK I changed the Page Component code from this

@Component({
selector: 'page',
templateUrl: './page.component.html'
    })
    export class PageComponent implements OnInit {
        alias: string;
        page:Page;

        constructor(private router:Router,
                    private route: ActivatedRoute,
                    private pageService:PageService) {

            this.route.params.subscribe(
                (params : Params) => {
                    this.alias = params["alias"];
                    console.log(this.alias)
                }
            );
        }

    ngOnInit():void {
            debugger;
            this.pageService.getPage(this.alias).subscribe(page => {
                this.page = page;
                console.log(this.page);
            });
        }
    }

to this one

@Component({
selector: 'page',
templateUrl: './page.component.html'
    })
    export class PageComponent implements OnInit {
        alias:string;
        page:Page;

        constructor(private router:Router,
                    private route:ActivatedRoute,
                    private pageService:PageService) {

            this.route.params.subscribe(
                (params:Params) => {
                    this.alias = params["alias"];
                    this.pageService.getPage(this.alias).subscribe(page => {
                        this.page = page;
                        console.log(this.page);
                    });
                    console.log(this.alias)
                }
            );
        }
         ngOnInit():void {
            this.pageService.getPage(this.alias).subscribe(page => {
                this.page = page;
                console.log(this.page);
            });
        }
    }