Binding a right context in ES6 class when using Q.nfcall

Question

I'm using Q package for an async call:

let loadPromise = Q.nfcall(m.loadObj,data);

m is an instance of this class:

class Base {

    constructor() {
        this._name = null;;
    }

    loadObj(data) {
        this._name = data;              
    }
}

The issue is that this is undefined after entering loadObj method.

As mentioned in Q wiki:

If you are working with methods, instead of simple functions, you can easily run in to the usual problems where passing a method to another function—like Q.nfcall—"un-binds" the method from its owner. To avoid this, you can either use Function.prototype.bind

How can I bind the right context to loadObj method ?

`loadObj` is not a [node-style callback function](https://github.com/kriskowal/q/wiki/API-Reference#interfacing-with-nodejs-callbacks) at all, it's not even asynchronous! You cannot use `nfcall` here! — Bergi, Sep 21 '16 at 19:09
@Bergi you right. I've just read it in the docs: "If you're working with functions that make use of the Node.js callback pattern, where callbacks are in the form of function(err, result), Q provides a few useful..." — ohadinho, Sep 22 '16 at 04:06

Stas Parshin · Answer 1 · 2016-09-21T18:36:20.770

0

As Q's doc states - you can use ninvoke to avoid un-binding like this:

let loadPromise = Q.ninvoke(m, 'loadObj', data);

Apparently, you can also do re-binding here:

let loadPromise = Q.nfcall(m.loadObj.bind(m), data);

edited Sep 21 '16 at 18:36

answered Sep 21 '16 at 18:08

Stas Parshin

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Binding a right context in ES6 class when using Q.nfcall

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