qwebs/lib/singleton.js

Web application framework

/*!
 * qwebs
 * Copyright(c) 2017 Benoît Claveau <benoit.claveau@gmail.com>
 * MIT Licensed
 */


"use strict";

let qwebs = null; //intance is store in the module to avoid reloading 
let lock = false;

class Singleton {

    /**
     * Singleton.init(() => new Qwebs({}))
     */
    static init(fn) {
        return Promise.resolve({}).then(() => {
            lock = true;
            if (qwebs) return;
            return fn().load().then(i => {
                qwebs = i;
            });
        }).then(() => {
            lock = false;
            return qwebs;
        }).catch(error => {
            lock = false;
            throw error;
        });
    }

    static set instance (value) { qwebs = value; }
    static get instance () { return qwebs; }
}

exports = module.exports = Singleton;