Value undefined after a function

Question

I have one class with one fuction in it, and another class that will import the first class and use that function. After the function operates i need one value, but i am not getting any value afte the function.

First class:

export class MoveEff {

    checkEffect(effectFaceOff1,moveEff1,moveEff2){
        if ( effectFaceOff1=== 'grassgrass') {

            moveEff1 = 10;
            console.log(moveEff1);

        }
    }
}

Second class :


import { Component, OnInit } from '@angular/core';
import {GenIService} from "../Pokemons/gen-i.service";
import {MovesService} from "../Moves/moves.service";
import {MoveDataClass} from "../MoveDATA/move-data-class";
import {MoveEff} from "../MoveDATA/move-eff";

@Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss'],
})

export class HomePage implements OnInit {

  effectFaceOff1;
  moveEff1;
  moveEff2;

constructor(private moveeff: MoveEff) {}

 this.moveeff.checkEffect(this.effectFaceOff1,this.moveEff1,this.moveEff2);

 console.log(this.moveEff1,this.moveEff2);

On the last console.log i should be seeing the 10 value of moveEff1, but it appears undefined.

Why? and how can i solve it?

The code is _not_ assigning a member field (it is a assigning to a global variable). Thus, “this.moveErf1” is not expected to be changed when accessed later. Other things might be wrong as well.. — user2864740, May 28 '20 at 23:38
JS doesn't pass references to primitive values; you cannot change variables passed like that. If you pass objects however, you can change them: https://jsfiddle.net/khrismuc/2xe3nc9m/ — , May 29 '20 at 08:28
Does this answer your question? [Pass Variables by Reference in Javascript](https://stackoverflow.com/questions/7744611/pass-variables-by-reference-in-javascript) — , May 29 '20 at 08:29

score 0 · Answer 1 · answered May 28 '20 at 23:36

0

Exporting the class may not be enough. Try exporting and importing all your methods as modules, or exporting the method directly.

answered May 28 '20 at 23:36

Unrefined

77
4

Should i import like this? "import {MoveEff.checkEffect} from "../MoveDATA/move-eff";" – Fábio Heitor May 28 '20 at 23:38
You could do that. Try putting the export keyword in front of your function. You should be able to access its values as JS classes aren't private. – Unrefined May 29 '20 at 00:05
Cant add the export , it doesnt allow me to – Fábio Heitor May 29 '20 at 00:11
If you still want to use the export keyword on you class, then add the 'static' keyword in front of your functions. That should do it. – Unrefined May 29 '20 at 00:14

S P · Answer 2 · 2020-05-28T23:43:58.623

i don't know where you are getting effectFaceOff1, moveEff1 and moveEff2 from, but if they are @Input, their values cannot be retrieved in the constructor.

In that case, you should move your code to the ngOnInit:

ngOnInit() {
  this.moveeff.checkEffect(this.effectFaceOff1,this.moveEff1,this.moveEff2);
  console.log(this.moveEff1,this.moveEff2);
}

Last but not least, MoveEff should be made an Injectable in order to provide it to your class:

@Injectable({ providedIn: 'root' })
export class MoveEff {
  checkEffect(effectFaceOff1,moveEff1,moveEff2){
    if ( effectFaceOff1 === 'grassgrass') {
        moveEff1 = 10;
        console.log(moveEff1);
    }
  }
}

Value undefined after a function

2 Answers2