Angular 8 CLI：如何使用提供程序延迟加载不可路由的功能模块

Question

So hey,

I tried to follow these guides: https://angular.io/guide/lazy-loading-ngmodules

But the official documentation only covers this with Router (just wow. Qngular docs are suboptimal)

https://netbasal.com/the-need-for-speed-lazy-load-non-routable-modules-in-angular-30c8f1c33093

So this medium article was exactly what I was searching for. My only problem is that it wont work.

ANGULAR.JSON

"architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            "lazyModules": [
              "path/to/components#MyModule"
            ],

APP MODULE

 providers: [
    SystemJsNgModuleLoader, // without this I get NullInjectorError
    CookieService,
    { provide: NgModuleFactoryLoader, useClass: SystemJsNgModuleLoader }, // this doesnt seem to do anything
    {
      provide: HTTP_INTERCEPTORS, useClass: AuthHeaderInterceptor, multi: true,
    }
  ],
  bootstrap: [AppComponent]

MODULE

@NgModule({
  imports: [
    CommonModule,
    MatButtonModule,
    MatIconModule,
  ],
  declarations: [
    MyModule.rootComponent
  ],
  providers: [MyService],
  entryComponents: [MyModule.rootComponent]
})
export class MyModule{
  static rootComponent = MyComponent;
  static forRoot(): ModuleWithProviders {
    return {
      ngModule: MyModule,
      providers: [MyService]
    };
  }
}

SERVICE

@Injectable()
export default class MyService {}
...

LAZY LOAD PROVIDER

export interface LAZY_MODULES {
  'MyModule': string;
}

export const lazyMap: LAZY_MODULES = {
  'MyModule': 'path/to/components#MyModule'
};

export const LAZY_MODULES_MAP = new InjectionToken('LAZY_MODULES_MAP', {
  factory: () => lazyMap
})

LAZY LOAD DIRECTIVE

@Directive({
  selector: '[lazyLoadModule]'
})
export class LazyLoadModuleDirective implements OnInit, OnDestroy {

  @Input('lazyLoadModule') moduleName: keyof LAZY_MODULES;
  private moduleRef: NgModuleRef<any>;

  constructor(
    private vcr: ViewContainerRef,
    private injector: Injector,
    private loader: NgModuleFactoryLoader,
    @Inject(LAZY_MODULES_MAP) private modulesMap
  ) { }

  ngOnInit() {
    this.loader
      .load(this.modulesMap[this.moduleName])
      .then((moduleFactory: NgModuleFactory<any>) => {
        this.moduleRef = moduleFactory.create(this.injector);
        const rootComponent = (moduleFactory.moduleType as ModuleWithRoot)
          .rootComponent;

        const factory = this.moduleRef.componentFactoryResolver.resolveComponentFactory(
          rootComponent
        );

        this.vcr.createComponent(factory);
      });
  }

  ngOnDestroy() {
    this.moduleRef && this.moduleRef.destroy();
  }
}

IN APP COMPONENT HTML

<ng-container *ngIf="showModule"
              lazyLoadModule="MyModule">
</ng-container>

so the result is:

1. If I am using th SystemJsNgModuleLoader without wrapper object, Chunking works (webpack reports that it build a path-to-components-my-module.ts ) In dev tools I get NullinjectorError for SystemJsNgModuleLoader

2. If I am using the SystemJsNgModuleLoader directly in providers I dont get an error in dev console. Chunking works also. But in network console, the module never gets loaded , even if i directly set showModule=true in app controller...

Answer 1

The above example worked. The guide was trivially assuming that everyone remembers to add the loader component the root module.

Interestingly no error was thrown, (because it is a directive, not an element) and the system just assumed that lazyLoadModule is a permitted HTML attribute? ANyway fixed by:

@NgModule({
  declarations: [
    ...,
    LazyLoadModuleDirective
  ]
  ...