State serialization in Cloud Code

Understand how Stateful Cloud Code serializes module state, and how to control or customize serialization behavior.

Read time 4 minutes

Last updated 2 months ago

Important

This page describes an experimental feature that might change significantly before release. It's not recommended to use or rely on experimental features in production environments due to potential instability.

Stateful Cloud Code automatically serializes and deserializes module class state between function invocations. Serialization allows class members to persist within the configured scope without manual storage management.

Understanding serialization behavior helps you design module classes and troubleshoot state persistence issues. Non-serialized fields and properties can still keep values in memory between invocations, but this behavior isn't guaranteed. Only serialized fields and properties persist reliably. The runtime can rehydrate object state from persisted data at any time.

Note

Stateful Cloud Code requires you to reference the following NuGet package versions in your modules:

```
com.unity.services.cloudcode.apis
```
v0.0.26 or later
```
com.unity.services.cloudcode.core
```
v0.0.4 or later

Default serialization behavior

By default, the runtime serializes module state using the following rules:

The runtime includes public fields and properties in the serialization.
The runtime excludes private fields and properties in the serialization.

This default inclusion of public members aligns with common serialization library conventions, making it familiar to developers who know standard .NET serialization patterns.


using System;using Unity.Services.CloudCode.Core;[StateScope(Scope.Player)]public class PlayerProgress{    // Serialized: public field    public int Level;    // Serialized: public property    public int Experience { get; set; }    // Not serialized: private field    private DateTime _lastCalculated;    // Not serialized: private property    private int CachedValue { get; set; }    [CloudCodeFunction("GetProgress")]    public string GetProgress()    {        return $"Level: {Level}, Experience: {Experience}";    }}

Serialization attributes

Use Cloud Code serialization attributes to explicitly control which members to include in the serialization.

Exclude public members from serialization

Apply

[CloudCodeIgnoreProperty]

to exclude a public field or property from serialization. Use this attribute for cached values, computed properties, or data that doesn't need to persist.

Tip

Use

[CloudCodeIgnoreProperty]

for computed or cached values to keep serialized state minimal. Only persist data that needs to survive between function calls.


using System.Collections.Generic;using Unity.Services.CloudCode.Core;[StateScope(Scope.Player)]public class PlayerInventory{    public List<string> Items = new List<string>();    // Excluded from serialization despite being public    [CloudCodeIgnoreProperty]    public int CachedItemCount;    [CloudCodeFunction("AddItem")]    public void AddItem(string item)    {        Items.Add(item);        CachedItemCount = Items.Count; // Recalculated anyway    }}

Include private members in serialization

Apply

[CloudCodeSerializeProperty]

to include a private field or property in serialization. Use this attribute to persist internal state while maintaining encapsulation.


using System.Collections.Generic;using Unity.Services.CloudCode.Core;[StateScope(Scope.MultiplayerSession)]public class GameSession{    // Included in serialization despite being private    [CloudCodeSerializeProperty]    private List<string> _playerIds = new List<string>();    // Included in serialization despite being private    [CloudCodeSerializeProperty]    private string _currentTurnPlayerId;    public int PlayerCount => _playerIds.Count;    [CloudCodeFunction("JoinSession")]    public string JoinSession(string playerId)    {        _playerIds.Add(playerId);        if (_playerIds.Count == 1)        {            _currentTurnPlayerId = playerId;        }        return $"Player {playerId} joined. {PlayerCount} players in session.";    }}

Custom serialization

For advanced scenarios, implement the

IStateSerializer

interface to control how the runtime serializes and deserializes your module state. This interface enables you to do the following:

Use a specific serialization library or format.
Handle complex types that require custom conversion logic.
Optimize serialization for performance or payload size.
Handle migration of persisted state after you deploy a new module version.

Important

If you change the structure of serialized data, ensure backward compatibility or implement migration logic using the

IStateSerializer

interface methods.

The IStateSerializer interface

The Cloud Code SDK provides the

IStateSerializer

interface. Implement this interface on your module class to replace the default serializer with your own behavior. The interface declares the following two methods:


namespace Unity.Services.CloudCode.Core{    public interface IStateSerializer    {        // Called to serialize the object state.        byte[] OnSerialize();        // Called to deserialize and restore object state.        void OnDeserialize(byte[] input);    }}

Tip

Test serialization independently. When using custom serializers, write unit tests to verify that your

OnSerialize

and

OnDeserialize

implementations work correctly outside the module runtime.

Custom serialization example with a third-party serializer

The following example demonstrates custom serialization using

Newtonsoft.Json

to serialize a game session's player list.

Important

Changes to serialization library behavior between module versions can change how the runtime stores and restores your state.


using System.Collections.Generic;using Newtonsoft.Json;using Newtonsoft.Json.Linq;using Unity.Services.CloudCode.Core;[StateScope(Scope.MultiplayerSession)]public class GameSession : IStateSerializer{    public List<string> _playerIds = new List<string>();    public string _hostPlayerId;    public byte[] OnSerialize()    {        var json = JsonConvert.SerializeObject(this);        return System.Text.Encoding.UTF8.GetBytes(json);    }    public void OnDeserialize(byte[] data)    {        var json = System.Text.Encoding.UTF8.GetString(data);        var serializer = JsonSerializer.Create();        serializer.Populate(JObject.Parse(json).CreateReader(), this);    }    [CloudCodeFunction("AddPlayer")]    public string AddPlayer(string playerId)    {        if (_playerIds.Count == 0)        {            _hostPlayerId = playerId;        }        _playerIds.Add(playerId);        return $"Player {playerId} joined. Host: {_hostPlayerId}";    }    [CloudCodeFunction("GetPlayers")]    public List<string> GetPlayers()    {        return _playerIds;    }}

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State serialization in Cloud Code

Default serialization behavior

Serialization attributes

Exclude public members from serialization

Include private members in serialization

Custom serialization

The IStateSerializer interface

Custom serialization example with a third-party serializer