ECMAScript 6 (ES6) importing problems


#21

@ganas
Be adviced, async is not supported on iOS.
I had to switch back to promises for iOS


#22

Yeah thats what I found out earlier on, and I decided not to use it for now until the both platforms are officially supported


#23

It’s correct that iOS doesn’t support async/await natively atm, but you can still use it. I’m using it in a production iOS app.

The trick is to include the __awaiter helper function. You need to include it only once, so main.ts makes sense (in case of an Angular project):

In my main.ts (and main.aot.ts) files I have: require('./async-helper'); before bootstrapping the app.

The content of async-helper.js is:

"use strict";
global.__awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
    return new (P || (P = Promise))(function (resolve, reject) {
        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
        step((generator = generator.apply(thisArg, _arguments || [])).next());
    });
};

global.__generator = (this && this.__generator) || function (thisArg, body) {
    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
    function verb(n) { return function (v) { return step([n, v]); }; }
    function step(op) {
        if (f) throw new TypeError("Generator is already executing.");
        while (_) try {
            if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
            if (y = 0, t) op = [0, t.value];
            switch (op[0]) {
                case 0: case 1: t = op; break;
                case 4: _.label++; return { value: op[1], done: false };
                case 5: _.label++; y = op[1]; op = [0]; continue;
                case 7: op = _.ops.pop(); _.trys.pop(); continue;
                default:
                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
                    if (t[2]) _.ops.pop();
                    _.trys.pop(); continue;
            }
            op = body.call(thisArg, _);
        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
    }
};

Note: make sure you don’t .gitignore this .js file.

This was all inspired by this excellent blogpost by @pana :kissing_heart:


#24

Will it work the same if I request this file in app.js
of my PAN app? @Eddy


#25

@multishiv19 Yep, you sure can. I just tested this in a PAN-TypeScript app (one of my plugin demo apps):

This is in (part of) main-view-model.ts:

  public async doSearchPrinters(): Promise<void> {
    const printers = await this.starPrinter.searchPrinters();
    console.log(`Printers: ${JSON.stringify(printers)}`);
  }

And this is (the entire) app.ts:

import * as application from 'tns-core-modules/application';
require('./async-helper');
application.start({ moduleName: "main-page" });

Note that if you don’t use TypeScript… then this is not possible as TS transpiles the async/await pair to use the provided polyfills like this:

    HelloWorldModel.prototype.doSearchPrinters = function () {
        return __awaiter(this, void 0, void 0, function () {
            var printers;
            return __generator(this, function (_a) {
                switch (_a.label) {
                    case 0: return [4, this.starPrinter.searchPrinters()];
                    case 1:
                        printers = _a.sent();
                        console.log("Printers: " + JSON.stringify(printers));
                        return [2];
                }
            });
        });
    };

Another excellent reason to use TypeScript imo.


#26

Ah! So, that’s the catch. Now I understand how that helper function works
Thanks for the details @Eddy :heart:


#27

Lol I got my hopes up until I got to the part where I need to use TypeScript.

Thanks for sharing