What is entryComponents in angular ngModule?

Question

I am working on an Ionic app ( 2.0.0-rc0 ) which depends on angular 2 . So the new introduction of ngModules is included.

Answer 1

A Bit of Background about entryComponent

entryComponent is any component Angular loads imperatively. You can declare entryComponent by bootstrapping it in NgModule or in route definitions.

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpClientModule,
    AppRoutingModule
  ],
  providers: [],
  bootstrap: [AppComponent] // bootstrapped entry component
})

Documentation says below

To contrast the two types of components, there are components which are included in the template, which are declarative. Additionally, there are components which you load imperatively; that is, entry components.

Now to answer your specific question about entryComponents

There is entryComponents array in @NgModule file. You can use this to add entryComponents if component is bootstrapped using ViewContainerRef.createComponent().

That is you're creating components dynamically and not by bootstrapping or in template.

const componentFactory = this.componentFactoryResolver.resolveComponentFactory(myComp.component);
const viewContainerRef = this.compHost.viewContainerRef;
viewContainerRef.clear();
const componentRef = viewContainerRef.createComponent(componentFactory);