是否可以访问 JavaScript 中另一个类中的类实例？

Question

I was trying to access an object instantiated inside a class, but something isn't working.

I have three classes: App, Map, Player

App class instantiated map class

 class App { constructor(canvas, sizeX, sizeY, sizeCase) { this.map = new Map(canvas, sizeX, sizeY, sizeCase); } }

Map

Inside Map class, is instantiated the Player class. My main problem, is that I can´t access the instance of Player to access to its methods

 class Map { constructor(canvas, sizeX, sizeY, sizeCase) { this.canvas = document.getElementById("canvas"); this.canvas.width = sizeX * sizeCase; this.canvas.height = sizeY * sizeCase; this.size = { x: sizeX, y: sizeY, case: sizeCase }; } setPlayers(quantity) { for (let index = 0; index < quantity; index++) { let x = App.random(this.size.x); let y = App.random(this.size.y); if (this.mapGame[x][y] == 0) { switch (index) { case 0: let player1 = new Player("vampi", 100, y, x); break; case 1: let player2 = new Player("wolfi", 100, y, x); break; default: break; } }else { console.log("Position occupied"); index--; } } } }

Player

 class Player { constructor(name, score, positionY, positionX) { this.name = name; this.score = score; } drawPlayer(playerImage) { app.map.mapGame[this.y][this.x] = 2; } }

Most of the questions I have read here are related to java, and the javascript ones I have found, are not related to my question, or I didn´t find the relation after reading them.

The console says:

"TypeError: app.map.player1 is undefined"

Answer 1

Variables are not the same as class properties. To make app.map.player1 work, you need to assign the property.

setPlayers(quantity) {
  for (let index = 0; index < quantity; index++) {
    let x = App.random(this.size.x);
    let y = App.random(this.size.y);
    if (this.mapGame[x][y] == 0) {
      switch (index) {
        case 0:
          this.player1 = new Player("vampi", 100, y, x);
          break;
        case 1:
          this.player2 = new Player("wolfi", 100, y, x);
          break;
        default:
          break;
      }
    } else {
      console.log("Position occupied");
      index--;
    }
  }
}