DataPersistenceManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.Linq;

public class DataPersistenceManager : MonoBehaviour
{
    [Header("File Storage Config")]
    [SerializeField] private string fileName;

    private GameData gameData;
    private List<IDataPersistence> dataPersistenceObjects;
    private FileDataHandler dataHandler;

    public static DataPersistenceManager instance { get; private set; }

    private void Awake()
    {
        if (instance != null)
        {
            Debug.LogError("Found more than one Data Persistence Manager in the scene.")
        };
        instance = this;
    }

    private void Start()
    {
        this.dataHandler = new FileDataHandler(Application.persistentDataPath, fileName);
        this.dataPersistenceObjects = FindAllDataPersistenceObjects();
        LoadGame();
    }

    public void NewGame()
    {
        this.gameData = new GameData();
    }

    public void LoadGame()
    {
        // load any saved data from a file using data handler
        this.gameData = dataHandler.Load();

        // if no data can be loaded, initialize to a new game
        if (this.gameData == null)
        {
            Debug.Log("Mo data was found. Initializing data to defaults");
            NewGame();
        }
        // push the loaded data to all other scripts that need it
        foreach (IDataPersistence dataPersistenceObj in dataPersistenceObjects) 
        {
            dataPersistenceObj.LoadData(gameData);
        }
        Debug.Log("Loaded game data");
    }

    public void SaveGame()
    {
        // pass the data to other scripts so they can update it
        foreach (IDataPersistence dataPersistenceObj in dataPersistenceObjects)
        {
            dataPersistenceObj.SaveData(ref gameData);
        }
        Debug.Log("Saved game data");

        // save that data to a file using data handler
        dataHandler.Save(gameData);
    }

    private void OnApplicationQuit()
    {
        SaveGame();
    }

    private List<IDataPersistence> FindAllDataPersistenceObjects()
    {
        IEnumerable<IDataPersistence> dataPersistenceObjects = FindObjectsOfType<MonoBehaviour>().OfType<IDataPersistence>();
        return new List<IDataPersistence>(dataPersistenceObjects);
    }
}