save-system

Save/Load System

Patterns for persisting game state to disk: an ISaveable interface for components that need persistence, a central SaveManager that orchestrates capture and restore, JSON serialization, save slot management, and preparation for cloud sync.

ISaveable Interface

Every component that needs to save state implements this interface. The SaveManager discovers all ISaveable objects in the scene and calls them during save/load.

/// <summary>
/// Implement on any MonoBehaviour that needs to persist state across saves.
/// </summary>
public interface ISaveable
{
    /// <summary>
    /// Unique key for this saveable. Must be stable across sessions.
    /// Recommended format: "{scene}_{gameobject}_{component}" or a GUID.
    /// </summary>
    string SaveKey { get; }

    /// <summary>
    /// Capture current state as a serializable object.
    /// Return a plain C# class or struct (no MonoBehaviour, no ScriptableObject).
    /// </summary>
    object CaptureState();

    /// <summary>
    /// Restore state from a previously captured object.
    /// Cast the object to the expected type.
    /// </summary>
    void RestoreState(object state);
}

Example: Saveable Health Component

using UnityEngine;

public class Health : MonoBehaviour, ISaveable
{
    [SerializeField] private int maxHealth = 100;
    [SerializeField] private string saveKey;

    private int _currentHealth;

    public string SaveKey => saveKey;

    private void Awake()
    {
        _currentHealth = maxHealth;
    }

    [System.Serializable]
    private struct HealthSaveData
    {
        public int currentHealth;
        public int maxHealth;
    }

    public object CaptureState()
    {
        return new HealthSaveData
        {
            currentHealth = _currentHealth,
            maxHealth = maxHealth
        };
    }

    public void RestoreState(object state)
    {
        if (state is HealthSaveData data)
        {
            _currentHealth = data.currentHealth;
            maxHealth = data.maxHealth;
        }
    }
}