Setting up and Referencing a Singleton in JS/US

Questions & Answers
1

I would like to set up a script that keeps track of the player’s health, wealth and current arms from scene to scene, as well as certain, scene specific information such as enemies killed that I otherwise know only how to relay between scripts/objects via SendMessage.

After looking around the Internet and Unity fora, I found recommendations of the use of a singleton script for problems that look similar to mine. I’ve run into two problems: 1.) Most of the example scripts are in C#, and I’m using UnityScript. 2.) I’m getting a recurring error message (“An instance of type ‘GameManagerClass’ is required to access non static member ‘IncreasePlayersMoney’.” where IncreasePlayersMoney is the singleton’s variable keeping track of how much money the player has accumulated.)

Here are the scripts (the first is the singleton; the second is the gameObject which is to report to the singleton by how much the player’s total wealth is to be increased).

Singleton:

class GameManagerClass
{
 private static var Instance : GameManagerClass = new GameManagerClass();
 static var PlayersGeld : int;
 
 public static function GetInstance() : GameManagerClass
 {
 if(Instance == null)
 
 Instance = new GameManagerClass();
 
 return Instance;
 }
 
 private function IncreasePlayersGeld (amount : int)
 {
 PlayersGeld += amount;
 Debug.Log("Geldsumme des Spielers :" + PlayersGeld);
 }
 
 private function GameManagerClass()
 {
 
 }
}

GameObject reporting to the singleton:

#pragma strict

function Start () {

}

function Update () {

}

function OnCollisionEnter(other : Collision)
{
 if(other.gameObject.tag == "Player")
 {
 var gameManagerRef : GameManagerClass = GameManagerClass.GetInstance();
 GameManagerClass.IncreasePlayersGeld(5);
 }
}
2

One purpose of the singleton is to prevent the use of static methods. Therefore you need to get a reference (GameManagerClass.GetInstance()) and call all methods (functions in JS/US) from this reference.

//Change this line
GameManagerClass.IncreasePlayersGeld(5);

//With
gameManagerRef.IncreasePlayersGeld(5);

Don’t create the singleton instance upon declaration.

// Change the line
private static var Instance : GameManagerClass = new GameManagerClass();

//With
private static var Instance : GameManagerClass = null;

And don’t use static members.

// Change the line
static var PlayersGeld : int;

/// With
var PlayersGeld : int;