Lazy Loading

States can be easily lazy-loaded by adding the provideStates function to the Route providers:

import { provideStates } from '@ngxs/store';

export const routes: Routes = [
  {
    path: '',
    component: AnimalsComponent,
    providers: [provideStates([AnimalsState])]
  }
];

If you are still using modules, you can import the NgxsModule using the forFeature method:

@NgModule({
  imports: [NgxsModule.forFeature([AnimalsState])]
})
export class LazyModule {}

It's important to note that when lazy-loading a state, it is registered in the global state, meaning this state object will now be persisted globally. Even though it's available globally, you should only use it within that feature component to ensure you don't create dependencies on things that may not be loaded yet.

How are feature states added to the global state graph? Assume you have a ZoosState:

@State<Zoo[]>({
  name: 'zoos',
  defaults: []
})
@Injectable()
export class ZoosState {}

And it's registered at the root level via provideStore([ZoosState]). Assume you've got a feature offices state:

@State<Office[]>({
  name: 'offices',
  defaults: []
})
@Injectable()
export class OfficesState {}

After the route is loaded and its providers are initialized, the global state will have the following signature if you register this state in some lazy-loaded component via provideStates([OfficesState]):

{
  zoos: [],
  offices: []
}

You can try it yourself by invoking store.snapshot() and printing the result to the console before and after the lazy component is loaded.