@aster-js/core

Lifecycle

Lazy

Lazy allow to get lazy references that will create the instance when its used not when its referenced.

class CustomService {
    constructor()  {
        console.debug("constructor");
    }
    hello() {
        console.debug("Hello!");
    }
}

const service = Lazy.get(
    () => new CustomService()),
    CustomService
);
console.debug("Reference to CustomService done!", service instanceof CustomService);
service.hello();

Output:

> Reference to CustomService done!, true
> constructor
> Hello!

See full documentation on Lazy

Disposable

Provide multiple way to reset objects or free handlers, resources or anything more safely using this disposable implementation.

function $on(target: EventTarget, name: string, callback: EventListener): IDisposable {
    target.addEventListener(name, callback);
    return IDisposable.create(() => target.removeEventListener(name, callback));
}

const @event = $on(document, "click", ()=> console.info("Click !"));

// ... later
IDisposable.safeDispose(@event);

See more about Disposable usage.

Metadata

Tag()

Attach metadata to Types and instances.

Declaration

// Local read-write tag
const apiUrlTag = Tag<string>("Api url");

// External read-only tag
export const ApiUrlTag = apiUrlTag.readOnly();

// Only way to add metadata will be using this decorator
export const apiUrl = (url: string) =>
    (target: Function) => apiUrlTag(target, url);

Tag Consumer

import { ApiUrlTag } from "./xxx";
// Tag Consumer
export class ApiClientBase {
    protected async getJson(relativeUrl: string): Promise<any> {
        // The metadata has been associated with the type
        // so we have to provide `this.constructor`
        const baseUrl = ApiUrlTag(this.constructor);

        const fullUrl = new URL(relativeUrl, baseUrl);
        const result = await fetch(fullUrl.toString());
        return await result.json();
    }
}

Usage

import { apiUrl, ApiClientBase } from "./xxx";

@apiUrl("https://my-api-client/v1/")
export class MyApiClient extends ApiClientBase {
    getData(): any{
        return this.getJson("/data");
    }
}

See more about Tag() or Tag.lazy()