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Save & Load System

The EntityManagerObject provides a flexible and lightweight save/load system based on JSON serialization. It is designed to handle large numbers of Entities and custom gameplay data in a simple and extensible way.

This page explains how to implement:

  • Multiple save slots
  • Custom game save data
  • Entity Manager API usage
  • Persistent save slot selection
  • Dirty flag optimization

Basic Save Architecture​

The save system is split into two parts:

  1. Entity Manager Data Handled automatically by the system, including:

  2. Extra Game Data (User-defined) Used for anything outside entity data, such as:

    • Player progression
    • Quest state
    • World flags
    • Settings
    • Save slot metadata You define this using a serializable class.

Creating Custom Save Data​

To store additional game-specific information, create a Serializable class:

[System.Serializable]
public class GameSaveData
{
    public int playerLevel;
    public float playTime;
    public string currentScene;
    public Vector3 playerPosition;
}

This data will be stored alongside Entity data as JSON.

Saving Data (Multiple Save Slots)​

You can support multiple save slots by using a save index:

public void Save(GameSaveData _data, int _saveIndex)
{
    string _extraString = JsonUtility.ToJson(_data);

    GameManager.EntityManagerData.Save(
        GameManager.GetFullSavePath("UserSave" + _saveIndex.ToString() + ".sav"),
        _extraString
    );
}

What happens here:

  • GameSaveData → converted to JSON
  • EntityManagerObject data is saved automatically
  • Both are stored in the same save file

Loading Data​

To load a save slot:

public void Load(int _saveIndex)
{
    string _extraString = GameManager.EntityManagerData.Load(
        GameManager.GetFullSavePath("UserSave" + _saveIndex.ToString() + ".sav")
    );

    GameSaveData _data =
        (GameSaveData)JsonUtility.FromJson(_extraString, typeof(GameSaveData));

    // Apply loaded data here
}

After loading:

Managing Save Slots​

A common approach is to store the last selected save slot:

Example workflow:

  1. Player selects Save Slot (0, 1, 2...)
  2. Store selected index in a separate config file or PlayerPrefs
  3. On game start:
    • Load last used save index
    • Call Load(saveIndex)

This allows seamless Continue Game functionality.

EntityManagerObject API Reference​

Saving & Loading​

public void ToJson(string _extraInfo) Converts all entities and extra info into a JSON string.

public string FromJson(string _json) Loads entity data from JSON and returns stored extra info.

Full Save System​

public void Save(string _path, string _extraInfo) Saves all entities + extra data to a file.

public string Load(string _path) Loads all entities + extra data from a file.

Single Entity Operations​

public string SingleEntityToJson(string _uid) Returns JSON for a single entity.

public void SaveSingleEntity(string _uid, string _path) Saves a single entity to a file.

public void LoadSingleEntity(string _uid, string _path) Loads a single entity from a file.

Performance Optimization (Dirty Flag)​

To improve performance in large projects, the Entity class includes a dirty flag:

public bool isDirty;

How it works:

  • isDirty = true → Entity has been modified
  • Your save logic can ignore unchanged Entities
  • Improves performance for large worlds

This reduces unnecessary serialization work in large projects.