As a beginner in the world of Angular, I have noticed various examples that utilize ngModule decorators above an empty class.
My question is: Is the class placed right after the ngModule decorator solely for initializing a module, or does it have additional functionalities?
If you want to trigger certain actions when a lazy loaded module is initialized, you can use the constructor or implement the ngDoBootstrap method.
In addition, injecting services into the constructor ensures that they are instantiated by Dependency Injection during the initialization of the application or lazy loaded modules.
There seem to be few other examples in this scenario besides utilizing the @NgModule() decorator and its information. It's possible that some additional code may be generated during app building process.
For more information on using the ngDoBootstrap method, refer to the comment on https://angular.io/guide/entry-components
It's essential to have the class declaration for proper utilization of the export functionality.
Even though the module starts with imports, you can still access the features provided by the class export (after all, why else would you be importing it?)
I hope this clarifies things for you.
EDIT --
"Although the body of the class may appear empty, the decorator (@NgModule) above it is what gives the class its capabilities. So technically, the class isn't really empty at all. It just doesn't require any additional logic once the decorator has been applied. When using bootstrapModule, it expects a class as input and assumes that said class has been decorated with @NgModule in a similar way to what you've done (including declarations, imports, providers, etc.)." source: Why Angular export empty class in app.modules.ts?
Check out the official documentation on Angular NgModules by visiting https://angular.io/guide/ngmodules
Here are some key points from the documentation:
@NgModule utilizes a metadata object to specify how to compile a component's templates and create an injector during runtime.
The NgModule metadata includes the following details:
In TypeScript, the class serves as a reference that can be imported for use. It is essential to have a class or member to decorate when using a decorator.
Once compiled, the annotation used to decorate the class will be retained. These annotations are utilized by Angular to configure the injector, determining which class should be created when a component needs to inject a specific member type.
You can add functionality to the constructor, such as performing actions when the module (and associated components/providers) are ready to be injected. This is one potential application for this feature.
[edit] Personally, I have utilized it to register a locale upon app startup.
export class AppModule {
constructor() {
registerLocaleData(localeDeCH);
}
}
This concept was inspired by this discussion, where the timing of calling registerLocaleData was not specified.
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