How to set instance property from a callback function invoked by the instance?

Question

I want to assign an attribute of an angular service with result comes from a callaback function I have this angular service:

@Injectable()
export class SkillsManagerService {

    private skill: any;
    private event: any;
    constructor() {
        // i have an event instance
        event = getEvent ();
        this.startWatching();
    }

    //function that start watching the event
    function startWatching() {
        event.watch(function(err, res) {
            // how to assign this.skill = res ?
        }
    });
}

Possible duplicate of [How to access the correct \`this\` inside a callback?](https://stackoverflow.com/questions/20279484/how-to-access-the-correct-this-inside-a-callback) — Jota.Toledo, May 08 '18 at 10:58
this isnt an issue related to angular IMO, is related to the language — Jota.Toledo, May 08 '18 at 10:59

score 1 · Accepted Answer · edited May 08 '18 at 11:18

1

Try using a lambda or "arrow function", which preserves the this context for the body. Here is a handy guide on when to use what: When should I use Arrow functions in ECMAScript 6?

function startWatching() {
    event.watch((err, res) => {
      this.skill = res;
    });
  }

edited May 08 '18 at 11:18

rinukkusu

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answered May 08 '18 at 10:56

Pardeep Jain

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it doesn't work, in fact "this" refer to the current object which is in this case the function startWatching.. – maroodb May 08 '18 at 10:58
Could you explain, what you changed and what it does differently? – rinukkusu May 08 '18 at 10:59
@maroodb using a lambda like in this answer should solve the problem – rinukkusu May 08 '18 at 10:59
it works! sorry I didn't realize the use of lambda in the answer. – maroodb May 08 '18 at 11:01
@rinukkusu , I have added `arrow function` instead of normal one, it should work i guess – Pardeep Jain May 08 '18 at 11:11

score 0 · Answer 2 · answered May 08 '18 at 11:01

0

Please convert ES6 function please read this link

 pulic function startWatching() {
     event.watch((err, res) => {
     this.skill = res 
   }
  });

answered May 08 '18 at 11:01

Sharma Vikram

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How to set instance property from a callback function invoked by the instance?

2 Answers2