Access variable from a different scene in Unity - unity3d

Question

I am fairly new to Unity and C# and am having some trouble. I am designing a 2d game, which has multiple levels. Each level contains a LevelManager which stores whether the level has been completed or not. They also have the DontDestroyOnLoad command in them. I want to access all the LevelManager gameObjects in my game and then store them in a level select scene. I want to use the win/lose bool to determine if the level has been completed so I can unlock the next level. To be clear, I want a way to access all the LevelManagers in my ENTIRE game and then store them as an array in a GameManager script. How do I do that?
Below is the LevelManager script which declares whether the level has been won or not.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
public class SceneController : MonoBehaviour
{
private GameObject[] StartHouseCount;
private GameObject[] StartDragonCount;
private GameObject[] LiveDragonCount;
private GameObject[] FinishedHouseCount;
public int NumOfHouses;
public int NumOfFinishedHouse;
public int NumOfDragons;
public int LiveNumOfDragons;
public GameObject[] Players;
public GameObject CurrentPlayer;
[Header("Player")]
public float RefuelRate;
public float RepairRate;
public GameObject canvas;
public bool GameIsPaused = false;
private GameObject MainPlayer;
public bool Win = false;
public int Level;
// Start is called before the first frame update
void Start()
{
CurrentPlayer = Players[0];
StartHouseCount = GameObject.FindGameObjectsWithTag("House");
StartDragonCount = GameObject.FindGameObjectsWithTag("Dragon");
NumOfHouses = StartHouseCount.Length;
NumOfDragons = StartDragonCount.Length;
MainPlayer = Players[0];
}
// Update is called once per frame
void Update()
{
GameIsPaused = canvas.GetComponent<PauseMenu>().GameIsPaused;
LiveDragonCount = GameObject.FindGameObjectsWithTag("Dragon");
LiveNumOfDragons = LiveDragonCount.Length;
FinishedHouseCount = GameObject.FindGameObjectsWithTag("ThankYou");
NumOfFinishedHouse = FinishedHouseCount.Length;
if (Input.GetKeyDown(KeyCode.Alpha1))
{
CurrentPlayer = Players[0];
}
if (Input.GetKeyDown(KeyCode.Alpha2))
{
CurrentPlayer = Players[1];
}
if (NumOfFinishedHouse == NumOfHouses)
{
SceneManager.LoadScene("WinScene");
}
if (MainPlayer == null)
{
SceneManager.LoadScene("LoseScene");
}
if (MainPlayer.GetComponent<BasicHelicopterController>().CurrentFuel <= 0 || MainPlayer.GetComponent<BasicHelicopterController>().CurrentHealth <= 0)
{
SceneManager.LoadScene("LoseScene");
}
}
}

Answer 1

You can create a ScoreManager script to store scores of each level using PlayerPrefs and attach this script to a GameObject in the first scene.
public class ScoreManager: MonoBehavior {
public static ScoreManager Instance;
const string LEVEL_KEY = "SCORE_";
const string MAX_LEVEL_KEY = "MAX_LEVEL";
public static int MAX_LEVEL {
get { return PlayerPrefs.GetInt(MAX_LEVEL_KEY, 1); }
set {
if(value > MAX_LEVEL) {
PlayerPrefs.SetInt(MAX_LEVEL_KEY, value);
}
}
}
void Awake() {
if(Instance != null) {
Destroy(this.gameObject);
return;
}
Instance = this;
DontDestroyOnLoad(this);
}
public void SaveScore(int level, float score) {
PlayerPrefs.SetFloat(LEVEL_KEY + level, score);
MAX_LEVEL = level;
}
public float GetScore(int level) {
return PlayerPrefs.GetFloat(LEVEL_KEY + level, 0);
}
public bool IsLevelUnlocked(int level) {
// You can write your own level-unlock logic here.
return level <= MAX_LEVEL;
}
...
}
Then you can just call its functions and properties from other scripts.
...
public void GameOver() {
ScoreManager.Instance.SaveScore(level, score);
}
...
Having all LevelManger scripts with DontDestroyOnLoad will cause a memory leak and sometimes it will affect the game performance.

Answer 2

First, DontDestroyOnLoad is not supposed to do this - main usage for this is to implement things like unity-singleton (easy-to-use template). It means, you`ll have one instance of levelManager, not one per level.
To do it in your way, you need to load all the scenes additively, and get all the LevelManager instances. Or you can load all scenes one-by-one, getting level name and it`s isPassed value from current LevelManager. It can take a while, and its a wrong way.
The right way is to store inter-scene data in ScriptableObject models. It`s like a MonoBehaviour, but not related to scene - it just lays somewhere in project.
So, in your case, you can create ScriptableObject called LevelProgress. It will store the list of all passed levels. It will have public method LevelPassed(string levelName), as a parameter you can use anything - levels name, levels index in build, scene itself, whatever. Every time, when player passes any level, your LevelManager (remove DontDestoryOnLoad from it), which has a reference to LevelProgress scriptable object, will call LevelProgress.LevelPasses(currentLevel). And then, if you need to know, was some level passed, or not, you can just check, is LevelProgress.PassedLevels list contains this level.
Additionally, you need to implement between-sessions persistance for this scriptable object. IMO, the best way for this is to use JSONUtility to convert ScriptableObject into JSON string, and then write it to PlayerPrefs.

Answer 3

I seemed to have figured it out. I created a gameObject containing a GameManagement script, that had the DontDestroyOnLoad line. I had also added a specific tag. I then searched for that object in each level and updated my values to that. The GameManagement script had an array of bools for levels completed and levels unlocked. Each levelmanager decided whether the level was won and updated that. Using that I determined what level was unlocked. I did though need to use Fire King's Awake Command. It ensures that there are no other copies of the script in the game. Solves my problems.