# Unity Data Persistence

> Robust Save/Load system using Data Binding, Serializable DTOs, and swappable Data Service backends (File/JSON default). Supports per-entity GUID identity for saving multiple actors (player, inventory, enemies).

- Skill: `muharremtozan/unity-data-persistence` (Agent Skill, multi-file: 6 files)
- Install (CLI): `npx skillmds@latest add muharremtozan/unity-data-persistence`
- Raw SKILL.md: https://api.skillmd.com/api/skills/muharremtozan/unity-data-persistence/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: muharremtozan (https://skillmd.com/u/muharremtozan)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/muharremtozan/unity-data-persistence

---


# Unity Data Persistence

Implement a professional Save/Load system built around **data binding**: saveable objects hold a live reference to a DTO that is always up-to-date, making serialization near-instant and backend-agnostic.

Inspired by [adammyhre/Unity-Inventory-System](https://github.com/adammyhre/Unity-Inventory-System/tree/master/Assets/_Project/Scripts/Persistence).

## Core Architecture

```
SaveLoadSystem
    ├── IDataService  (FileDataService by default)
    │       └── ISerializer  (JsonSerializer by default)
    └── GameData  (your root DTO)
            ├── PlayerData   (ISaveable) ←─ Hero.Bind()
            └── InventoryData (ISaveable) ←─ Inventory.Bind()
```

## Core Features

1. **Data Binding Pattern**: MonoBehaviours hold a reference to their own DTO, so saving is just serializing GameData — no polling, no property walking.
2. **IBind\<T\> / ISaveable**: Two interfaces that wire scene entities to their save data at scene load time.
3. **SerializableGuid**: Stable, fast GUID identity (int-based comparison) for matching saved data to spawned entities.
4. **Swappable Backend**: `IDataService` + `ISerializer` let you change from local JSON to Cloud/Binary with a one-line change.
5. **Multi-Entity Binding**: List-based `Bind<T, TData>(List<TData>)` handles many-entity scenarios (enemies, spawners).

## Core Files (Max 3)

- `PersistenceCore.cs.txt` — `ISerializer`, `JsonSerializer`, `IDataService`, `ISaveable`, `IBind<T>`, `SerializableGuid`
- `FileDataService.cs.txt` — Local disk implementation: Save, Load, Delete, DeleteAll, ListSaves
- `SaveLoadSystem.cs.txt` — Persistent MonoBehaviour orchestrator with `Bind<T,TData>()` and public Save/Load/New API

## Usage

### Quick Start (Light Path — no binding needed)
```csharp
// 1. Extend GameData with your fields
[Serializable] public class GameData {
    public string Name;
    public int Score;
}

// 2. Save / Load
SaveLoadSystem.Instance.gameData.Score = 100;
SaveLoadSystem.Instance.SaveGame();
SaveLoadSystem.Instance.LoadGame("MySave");
```

### Full System (Pro Path — data binding)
```csharp
// 1. Create a DTO
[Serializable] public class PlayerData : ISaveable {
    [field: SerializeField] public SerializableGuid Id { get; set; }
    public Vector3 position;
}

// 2. Implement IBind on your MonoBehaviour
public class PlayerEntity : MonoBehaviour, IBind<PlayerData> {
    [SerializeField] SerializableGuid id;
    PlayerData data;
    public SerializableGuid Id { get => id; set => id = value; }
    public void Bind (PlayerData d) { data = d; data.Id = id; transform.position = d.position; }
    void Update () { data.position = transform.position; } // write-through
}

// 3. Register in SaveLoadSystem.OnSceneLoaded
Bind<PlayerEntity, PlayerData>(gameData.playerData);
```

See `references/guide.md` for complete examples including multi-entity binding and backend swapping.

## Key Principle

Design your data model first. The DTO structure IS your save format. Start simple (`GameData` with flat fields) — add binding only when entities need independent, restorable state.