Lazy load module in angular 8

Question

I have a dashboard app where I was lazy loading widgets (not tied to a route).

I was doing this by defining an object {name: string, loadChildren: string}

Answer 1

In Angular 8 the result of loadChildren function is either Promise of NgModule type in JIT mode or Promise of NgModuleFactory in AOT mode.

With this in mind you can rewrite your service as follows:

import { 
    Injectable, Compiler, Injector, Type, 
    ViewContainerRef, ComponentFactoryResolver,
    NgModuleFactory, Inject 
} from '@angular/core';

@Injectable()
export class LazyLoaderService {

  constructor(private injector: Injector,
    private compiler: Compiler,
    @Inject(LAZY_WIDGETS) private lazyWidgets: 
       { [key: string]: () => Promise<NgModuleFactory<any> | Type<any>> }) { }


  async load(name: string, container: ViewContainerRef) {
    const ngModuleOrNgModuleFactory = await this.lazyWidgets[name]();
 
    let moduleFactory;

    if (ngModuleOrNgModuleFactory instanceof NgModuleFactory) {
      // aot mode
      moduleFactory = ngModuleOrNgModuleFactory;
    } else {
      // jit mode
      moduleFactory = await this.compiler.compileModuleAsync(ngModuleOrNgModuleFactory);
    }

    const entryComponent = (<any>moduleFactory.moduleType).entry;
    const moduleRef = moduleFactory.create(this.injector);

    const compFactory = moduleRef.componentFactoryResolver.resolveComponentFactory(entryComponent);

    const comp = container.createComponent(compFactory);
  }   
}

Stackblitz Example

Tip: Always look at the source code when you're in doubt

• https://github.com/angular/angular/blob/72ecc453639eae017f75653c9004adc406ed2ee6/packages/router/src/router_config_loader.ts#L46-L59

• https://github.com/angular/angular/blob/32886cf9ace539e14e2b387cd8afb10715c8d3de/aio/src/app/custom-elements/elements-loader.ts#L56-L68

Answer 2

It seems that when using Router, lazyWidgets const should have not name but path property:

export const lazyWidgets: { path: string, loadChildren: () => .....

Otherwise you'll get error:

Invalid configuration of route '': routes must have either a path or a matcher specified