Javascript - Can't get the value of the function outside of it, getting undefined

Question

I am willing to get the value of the function outside of it; however, I am getting undefined here is the below code:

getCoords() {
  let call = this.http.get('https://maps.googleapis.com/maps/api/geocode/json?address=' + address + '&key=' + this.key).subscribe(data => {

    let lat = data.json().results[0].geometry.location.lat;
    let long = data.json().results[0].geometry.location.lng;

    this.latLong = {
      "lat": lat,
      "long": long
    };

    //I can get it here
    console.log('called >> ', this.latLong)

    return this.latLong;

  });

  //this.latlong is undefined !
}

//if I call getCoords() here I get undefined too

No value is returned from `getCoords` function. What does `.subscribe()` return? — guest271314, May 14 '17 at 15:05
Are you sure that `data` variable which you get after calling the URL is not `undefined` too? — errata, May 14 '17 at 15:05
The `subscribe` method is clearly **asynchronous**, hence the callback — adeneo, May 14 '17 at 15:09

guest271314 · Answer 1 · 2017-05-14T15:43:46.183

2

If subscribe returns a Promise, return call, chain .then() to get the value this.latLong returned from within .subscribe()

getCoords() {
  let url = 'https://maps.googleapis.com/maps/api/geocode/json?address=' 
             + address + '&key=' + this.key;
  let call = new Promise((resolve, reject) => {
    this.http.get(url).subscribe(data => {

      let lat = data.json().results[0].geometry.location.lat;
      let long = data.json().results[0].geometry.location.lng;

      this.latLong = {
        "lat": lat,
        "long": long
      };

      //I can get it here
      console.log('called >> ', this.latLong)

      resolve(this.latLong);

    });
  });

  return call.then(res => { console.log(res); return res })
  //this.latlong is undefined !
}

getCoords()
.then(data => console.log(data))
.catch(err => console.log(err));

edited May 14 '17 at 15:43

answered May 14 '17 at 15:10

guest271314

1
15
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Tried that; however, it throws an error saying that '.then' does not exist on type Subscription – Folky.H May 14 '17 at 15:19
What does `.subscribe()` return? – guest271314 May 14 '17 at 15:26
`.subscribe()` is an observable that takes tree parameters `.subscribe(success, failure, complete)` – Folky.H May 14 '17 at 15:31
You can use `Promise` constructor to call `resolve()` within `success` or `reject` within `failure`, return the `Promise` constructor from call. See updated post – guest271314 May 14 '17 at 15:41
this one `return call.then(res => { console.log(res); return res })` replaced `undefined` by `__zone_symbol__state` which I don't know from where it came. For the last line `getCoords().then()` says that `property` then does not exists on type `void` – Folky.H May 14 '17 at 15:52
You need to include more details at Question. What is `__zone_symbol__state` ? Can you reproduce issue at plnkr https://plnkr.co? See https://stackoverflow.com/help/mcve – guest271314 May 14 '17 at 15:58
I, myself don't know it, I believe it came from `Promise` constructor – Folky.H May 14 '17 at 16:00

score 0 · Answer 2 · answered May 14 '17 at 15:10

0

Sure, because http.get is async method so the callback function (subscribe) will call after the line this.latlong will call, so in that time this.latlong is undefined.

answered May 14 '17 at 15:10

Mosh Feu

28,354
16
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pretty logical, but how can I retrieve that value? – Folky.H May 14 '17 at 15:22
You have to do this **inside** the `subscribe` callback – Mosh Feu May 14 '17 at 15:30
Can you please be clear, an example will be very helpful – Folky.H May 14 '17 at 15:32
Just like the answer above, if you don't understand, let me know.. – Mosh Feu May 16 '17 at 04:58

Javascript - Can't get the value of the function outside of it, getting undefined

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