Why is the "bootstrap" key in @NgModule an array?
According to my knowledge, there can only be one entry point for an application. As shown in the below code snippet, we pass an array in the bootstrap key that defines the entry point of the application.
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
@NgModule({
declarations: [AppComponent, MyComboboxComponent,
CollapsibleDirective, CustomCurrencyPipe],
imports: [BrowserModule],
providers: [UserService, LessonsService],
bootstrap: [AppComponent]
})
export class AppModule {
}
PS: I am learning Angular 2 and the question may sound silly :)
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You can transfer as many boot components as you like. You just end up with several independent components:
bootstrap: [AComponent, BComponent]
RootModuleInjector
|
|
ApplicationRef.views
/ \
/ \
AComponent BComponent
Also see What are the implications of self-tuning multiple components
When you run change detection, Angular will run change detection for each tree separately:
class ApplicationRef {
tick(): void {
...
try {
this._runningTick = true;
// here this._views.length equals to 2
this._views.forEach((view) => view.detectChanges());
You can even add a new root component ApplicationRef
manually if you like:
const componentRef = componentFactoryResolver.resolveComponentFactory(SomeComponent)
applicationRef.attachView(componentRef.hostView);
RootModuleInjector
|
|
ApplicationRef.views
/ | \
/ | \
AComponent SomeComponent BComponent
If you need to share some data between root components, you can define the provider of the root module that will be used to create the RootModuleInjector:
@NgModule({
providers: [ServiceSharedBetweenRootComponents]
}
export class AppModule {}
And then you can inject it into each root component:
export class AComponent {
constructor(service: ServiceSharedBetweenRootComponents)
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there can be only one application entry point
Not. You can create multiple components as entry points in your application.
Example: fooobar.com/questions/229923 / ...
Here is an example of how we can communicate between root components
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