evt/src/tools/Deferred.ts

Type safe replacement for node's EventEmitter

import { overwriteReadonlyProp } from "tsafe/lab/overwriteReadonlyProp";

export class Deferred<T> {

    public readonly pr: Promise<T>;

    /** NOTE: Does not need to be called bound to instance*/
    public readonly resolve: (value: T)=> void;
    public readonly reject: (error: any)=> void;

    constructor() {

        let resolve!: (value: T)=> void;
        let reject!: (error: any)=> void;

        this.pr = new Promise<T>(
            (resolve_, reject_) => {

                resolve = value => {

                    overwriteReadonlyProp(this, "isPending", false);
                    resolve_(value);

                };

                reject = error => {


                    overwriteReadonlyProp(this, "isPending", false);
                    reject_(error);

                };

            }
        );

        this.resolve = resolve;
        this.reject = reject;

    }


    public readonly isPending: boolean = true;


}

export namespace Deferred {

    export type Unpack<T extends Deferred<any>> = T extends Deferred<infer U> ? U : never;

}

export class VoidDeferred extends Deferred<undefined>{

    declare public readonly resolve: () => void;

}