Uncaught (in promise): TypeError: Cannot read property 'component' of null

Question

Getting this error when trying to use nestet route in Angular 4:

ERROR Error: Uncaught (in promise): TypeError: Cannot read property \'component\' of null
Ty         


        

Answer 1

Just thought I'd add a comment for the benefit of those who stumble across this for the same reason I did. If your template uses conditional rendering, and those conditions are satisfied asynchronously, the router-outlet cannot be inside the conditional markup because the framework might try to render the markup before the condition is satisfied. For example:

<div *ngIf="someAsyncCall()">
   <header>{{some result from the async call}}</header>
   <router-outlet></router-outlet>
</div>

may fail depending on how quickly the async call finishes. It's always safer to include only the static parts of a the markup in the conditional rendering. As in:

<div *ngIf="someAsyncCall()">
    <header>{{some result from the async call}}</header>
</div>
<router-outlet></router-outlet>

I got bit by wrapping the entire page in a "busy indicator" directive which pretty much guaranteed that the router-outlet would not be available all the time. Seems obvious in hindsight, but....

Answer 2

If anyone interested in going with Child route structure. You could follow this model. I found this in ngx-breadcrumbs.

const myRoutes : Route[] = {
  {
    path: '',
    component: HomeComponent        
  },
  {
    path: 'about',
    component: AboutComponent        
  },
  {
    path: 'person',
    children: [
      {
          path: '',
          component: PersonListComponent
      },
      {
          path: ':id',
          component: PersonDetailComponent              
      } 
    ]
  },    
  {
    path: 'folder',        
    children: [
      {
      path: '',
      component: FolderComponent
      },
      {
        path: ':id',
        component: FolderComponent            
      }
    ]
  }
};

Answer 3

As this article (https://angular-2-training-book.rangle.io/handout/routing/child_routes.html) states when dealing with child routes, just as you define a router-outlet for the root of your application, you must define a router-outlet for your parent component (in this case the ConcursoItemComponent. And technically also the CargoItemComponent & DisciplinaItemComponent) So you have 2 options.

• Define a router-outlet in the ConcursoItemComponent. This way the router will know where to load the child component (CargoItemComponent) when the user visits c/:concurso/:cargo
• Don't use child routes and instead make all of your routes at the top router level (root of the application)

{
    path: 'c/:concurso,
    component: ConcursoItemComponent
},
{
    path: 'c/:concurso/:cargo,
    component: CargoComponent
},
{
    path: 'c/:concurso/:cargo/:disc,
    component: DisciplinaItemComponent
},
{
    path: 'c/:concurso/:cargo/:disc/:assunto,
    component: AssuntoItemComponent
}

This way the router will always insert the component into the router-outlet at the root of the application.