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lithium-angular-example-app

Live Demo

A simple TODO list app built with Angular and @lithiumjs/angular.

This project was created to demonstrate how Lithium for Angular enables creating performant Angular components with very little boilerplate by fully leveraging Observables and Zone-less change detection. The project also makes use of other libraries like ngxs/store to show how Lithium integrates with other libraries.

This project was generated with Angular CLI.

Running the app

Run ng serve for a dev server. Navigate to http://localhost:4200/. The app will automatically reload if you change any of the source files.

Building the app

Run ng build to build the project. The build artifacts will be stored in the dist/ directory. Use the --prod flag for a production build.

To get more help on the Angular CLI use ng help or go check out the Angular CLI README.

Using the app

This is a basic todo list app that allows you to register a user (or multiple users) and manage multiple todo lists per user.

Features:

• Create user accounts and save your todo data.
• Create and manage multiple todo lists and track completed tasks.
• Full session and state mangement.
• Serialization and deserialization of user and session data (via your own browser's local storage).
• Responsive UI design using Angular Material.

To use the app, you must first register a user. Once you have created a user, you will be redirected to the homepage, where you can start creating and managing todo lists.

The code - Points of interest

The application is fully Zone-less via the use of provideExperimentalZonelessChangeDetection(). All change detection is handled automatically by Lithium via AutoPush. This is enabled in BaseComponent, the common base class for all components in the app:

export class BaseComponent {

    constructor(
        protected readonly injector: Injector,
        cdRef?: ChangeDetectorRef
    ) {
        if (cdRef) {
            // Enables automatic push-based change detection for this class:
            AutoPush.enable(this, cdRef);
        }
    }
}

The project contains several components that showcase common use cases that you may encounter when writing an Angular application and how Lithium for Angular can be used effectively in these scenarios. Several examples are:

Basic usage of ComponentState and ComponentStateRef

There are many usages of ComponentState and ComponentStateRef in the application. One example is the HomeComponent:

...

public showNewListNameInput = false;

...

constructor(
    stateRef: ComponentStateRef<HomeComponent>
) {
    // Wait for showNewListNameInput to become true...
    stateRef.get('showNewListNameInput').pipe(
        filter(Boolean),
        delay(100)
    ).subscribe(() => this.newListNameInput.nativeElement.focus()); // Focus the input box

    ...
}

Using ComponentStateRef in base component classes

The EntryBasePage class is a base component class that makes use of ComponentStateRef:

...

constructor() {
    const stateRef = injector.get<ComponentStateRef<EntryBasePage>>(ComponentStateRef);

    stateRef.get("error").pipe(
        filter<string>(Boolean)
    ).subscribe(error => {
        console.error(error);
        snackBar.open(error, 'Dismiss', { verticalPosition: 'top' });
    });

    ...
}

Using @AsyncState to alias external observables

The HomeComponent makes use of the @AsyncState decorator to create a synchronous alias of an external state Observable from NGXS:

class HomeComponent {
    ...

    public readonly user$!: Observable<User> = this.store.select(SessionState.getUser);

    // `user` automatically receives all emissions from `user$`
    @AsyncState()
    public user!: User;

    ...

    constructor() {
        ...

        this.onListChanged$.subscribe(() => store.dispatch(new UpdateUserAction(this.user)));
    }
}

Using @DeclareState to enable observation of undeclared properties

The TodoListViewComponent uses the @DeclareState decorator to declare an undeclared property to Lithium:

class TodoListViewComponent extends BaseComponent {

    @Input()
    @DeclareState()
    public list!: TodoList;

    ...
}