TheOne Studio Unity Development Standards

⚠️ Unity 6 (C# 9): All patterns and examples are compatible with Unity 6, which uses C# 9. No C# 10+ features are used.

Skill Purpose

This skill enforces TheOne Studio's comprehensive Unity development standards with CODE QUALITY FIRST:

Priority 1: Code Quality & Hygiene (MOST IMPORTANT)

• Nullable reference types, access modifiers, fix all warnings
• Throw exceptions (never log errors)
• TheOne.Logging.ILogger (runtime, no guards, no prefixes, no constructor logs) vs Debug.Log (editor only)
• readonly/const, nameof, using directive scope
• No inline comments (use descriptive names)

Priority 2: Modern C# Patterns

• LINQ over loops, extension methods, expression bodies
• Null-coalescing operators, pattern matching
• Modern C# features (records, init, with)

Priority 3: Unity Architecture

• VContainer + SignalBus OR TheOne.DI + Publisher/Subscriber
• Data Controllers pattern (NEVER direct data access)
• Resource management, UniTask async patterns

Priority 4: Performance & Review

• LINQ optimization, allocation prevention
• Code review guidelines

When This Skill Triggers

• Writing or refactoring Unity C# code
• Implementing Unity features with dependency injection
• Working with events and signals
• Accessing or modifying game data
• Reviewing code changes or pull requests
• Setting up project architecture

Quick Reference Guide

What Do You Need Help With?

Priority	Task	Reference
🔴 PRIORITY 1: Code Quality (Check FIRST)
1	Nullable types, access modifiers, warnings, exceptions	Quality & Hygiene ⭐
1	TheOne.Logging.ILogger (no guards, no prefixes, no constructor logs) vs Debug.Log	Quality & Hygiene ⭐
1	readonly/const, nameof, using scope, no inline comments	Quality & Hygiene ⭐
🟡 PRIORITY 2: Modern C# Patterns
2	LINQ, extension methods, var usage	LINQ Patterns
2	Expression bodies, null-coalescing, pattern matching	Modern C# Features
2	Records, init, with expressions	Modern C# Features
🟢 PRIORITY 3: Unity Architecture
3	VContainer dependency injection	VContainer DI
3	SignalBus event system	SignalBus Events
3	Data Controllers pattern (NEVER direct data access)	Data Controllers
3	Service/Bridge/Adapter integration	Integration Patterns
3	TheOne.DI + Publisher/Subscriber alternative	TheOne Framework
3	UniTask async/await patterns	UniTask Patterns
🔵 PRIORITY 4: Performance & Review
4	Performance, LINQ optimization, allocations	Performance
4	Architecture review (DI, events, controllers)	Architecture Review
4	C# quality review (LINQ, null handling)	C# Quality
4	Unity-specific review (components, lifecycle)	Unity Specifics
4	Performance review (allocations, hot paths)	Performance Review

🔴 CRITICAL: Code Quality Rules (CHECK FIRST!)

⚠️ MANDATORY QUALITY STANDARDS

ALWAYS enforce these BEFORE writing any code:

1. Enable nullable reference types - No nullable warnings allowed
2. Use least accessible access modifier - private by default
3. Fix ALL warnings - Zero tolerance for compiler warnings
4. Throw exceptions for errors - NEVER log errors, throw exceptions
5. TheOne.Logging.ILogger for runtime - No conditional guards (#if), no prefixes ([prefix]), NEVER in constructors; Debug.Log ONLY for editor scripts
6. Use readonly for fields - Mark fields that aren't reassigned
7. Use const for constants - Constants should be const, not readonly
8. Use nameof for strings - Never hardcode property/parameter names
9. Using directive in deepest scope - Method-level using when possible
10. No inline comments - Use descriptive names; code should be self-explanatory

Example: Enforce Quality First

// ✅ EXCELLENT: All quality rules enforced
#nullable enable // 1. Nullable enabled

public sealed class PlayerService
{
    private readonly TheOne.Logging.ILogger logger;
    private const int MaxHealth = 100;

    public PlayerService(TheOne.Logging.ILogger logger)
    {
        this.logger = logger;
    }

    public Player GetPlayer(string id)
    {
        using System.Text.Json;

        return players.TryGetValue(id, out var player)
            ? player
            : throw new KeyNotFoundException($"Player not found: {id}");
    }

    private void LoadGameData()
    {
        this.logger.Info("Game data loaded");
    }
}

#if UNITY_EDITOR
public class EditorTool
{
    public void Process()
    {
        Debug.Log("Processing..."); // 5. Debug.Log OK in editor
    }
}
#endif

⚠️ Unity Architecture Rules (AFTER Quality)

Choose ONE Framework Stack

Choose ONE stack per project:

Option 1: VContainer + SignalBus

• ✅ VContainer for dependency injection
• ✅ SignalBus for events
• ✅ [Preserve] attribute on constructors

Option 2: TheOne.DI + Publisher/Subscriber

• ✅ TheOne.DI wrapper
• ✅ IPublisher/ISubscriber for events
• ✅ [Inject] attribute on constructors

Universal Rules (Both Stacks):

• ✅ Use Data Controllers (NEVER direct data access)
• ✅ Use UniTask for async operations
• ✅ Unload assets in Dispose
• ✅ TheOne.Logging.ILogger for runtime (no guards, no prefixes, no constructor logs), Debug.Log for editor only

Brief Examples

🔴 Code Quality First

// ✅ EXCELLENT: Quality rules enforced
#nullable enable

public sealed class PlayerController
{
    private readonly TheOne.Logging.ILogger logger;
    private const int MaxRetries = 3;

    public PlayerController(TheOne.Logging.ILogger logger)
    {
        this.logger = logger;
    }

    public Player LoadPlayer(string id)
    {
        if (!File.Exists(id))
            throw new FileNotFoundException($"Player file not found: {id}");

        this.logger.Info($"Loading player {id}");
        return DeserializePlayer(id);
    }
}

#if UNITY_EDITOR
public class EditorHelper
{
    public void Log() => Debug.Log("Editor only"); // Debug.Log OK in editor
}
#endif

🟡 Modern C# Patterns

// ✅ GOOD: LINQ instead of loops
var activeEnemies = allEnemies.Where(e => e.IsActive).ToList();

// ✅ GOOD: Expression bodies
public int Health => this.currentHealth;

// ✅ GOOD: Null-coalescing
var name = playerName ?? "Unknown";

// ✅ GOOD: Pattern matching
if (obj is Player player) player.TakeDamage(10);

Unity Architecture (VContainer)

using UnityEngine.Scripting;
using VContainer.Unity;

public sealed class GameService : IInitializable, IDisposable
{
    private readonly SignalBus signalBus;
    private readonly LevelDataController levelController;

    [Preserve]
    public GameService(SignalBus signalBus, LevelDataController levelController)
    {
        this.signalBus = signalBus;
        this.levelController = levelController;
    }

    void IInitializable.Initialize()
    {
        this.signalBus.Subscribe<WonSignal>(this.OnWon);
    }

    void IDisposable.Dispose()
    {
        this.signalBus.TryUnsubscribe<WonSignal>(this.OnWon);
    }
}

Unity Architecture (TheOne.DI)

public sealed class GameService : IAsyncEarlyLoadable, IDisposable
{
    private readonly IPublisher<WonSignal> publisher;
    private IDisposable? subscription;

    [Inject]
    public GameService(
        IPublisher<WonSignal> publisher,
        ISubscriber<WonSignal> subscriber)
    {
        this.publisher = publisher;
        this.subscription = subscriber.Subscribe(this.OnWon);
    }

    public void Dispose()
    {
        this.subscription?.Dispose();
    }
}

Code Review Checklist

Quick Validation (before committing)

🔴 Code Quality (CHECK FIRST):

• Nullable reference types enabled (#nullable enable)
• All access modifiers correct (private by default)
• Zero compiler warnings
• Exceptions thrown for errors (no error logging)
• TheOne.Logging (runtime) vs Debug.Log (editor only)
• readonly used for non-reassigned fields
• const used for constants
• nameof used instead of string literals
• Using directives in deepest scope
• No inline comments (self-explanatory code)

🟡 Modern C# Patterns:

• LINQ used instead of manual loops
• Expression bodies for simple members
• Null-coalescing operators used
• Pattern matching for type checks
• Modern C# features used where appropriate

🟢 Unity Architecture:

• VContainer/TheOne.DI used correctly
• SignalBus/Publisher-Subscriber used correctly
• Data accessed through Controllers only
• All signals unsubscribed in Dispose
• [Preserve] or [Inject] attribute on constructors

🟢 Unity Specifics:

• Assets loaded are unloaded in Dispose
• No Find/GetComponent in Update/runtime loops
• TryGetComponent used instead of GetComponent + null check
• Lifecycle methods in correct order

🔵 Performance:

• No allocations in Update/FixedUpdate
• LINQ avoided in hot paths
• .ToArray() used instead of .ToList() when not modified

Common Mistakes to Avoid

❌ DON'T:

1. Ignore nullable warnings → Enable #nullable and fix all warnings
2. Log errors instead of throwing → Throw exceptions for errors
3. Use Debug.Log in runtime code → Use TheOne.Logging.ILogger (Debug.Log is editor only)
4. Add conditional guards to logs → ILogger handles #if internally
5. Add manual log prefixes → ILogger handles [prefix] automatically
6. Log in constructors → Never log in constructors (keep fast/side-effect free)
7. Use logger?.Method() → Use logger.Method() (DI guarantees non-null)
8. Add verbose logs → Keep only necessary logs
9. Skip access modifiers → Always use least accessible (private default)
10. Hardcode strings → Use nameof() for property/parameter names
11. Leave fields mutable → Use readonly/const where possible
12. Use Zenject → Use VContainer
13. Use MessagePipe directly → Use SignalBus
14. Access data models directly → Use Controllers
15. Forget to unsubscribe from signals → Implement IDisposable
16. Add inline comments → Use descriptive names instead

✅ DO:

1. Enable nullable reference types (#nullable enable)
2. Throw exceptions for errors (never log errors)
3. Use TheOne.Logging.ILogger for runtime (no guards, no prefixes, no constructor logs)
4. Use logger.Method() directly (no null-conditional, DI guarantees non-null)
5. Debug.Log for editor only (#if UNITY_EDITOR)
6. Use least accessible modifiers (private by default)
7. Use descriptive names (no inline comments)
8. Use nameof() for string literals
9. Use readonly/const for immutable fields
10. Use VContainer or TheOne.DI for dependency injection
11. Use SignalBus or Publisher/Subscriber for all events
12. Use Controllers for all data access
13. Always implement IDisposable and unsubscribe
14. Add [Preserve] or [Inject] to prevent code stripping
15. Use LINQ for collection operations

Review Severity Levels

🔴 Critical (Must Fix)

• Nullable warnings not fixed - Enable #nullable and fix all warnings
• Logging errors instead of throwing - Use throw, not log for errors
• Debug.Log in runtime code - Must use TheOne.Logging.ILogger (Debug.Log = editor only)
• Conditional guards on logs - ILogger handles #if internally, remove guards
• Manual log prefixes - ILogger handles [prefix] automatically, remove prefixes
• Logging in constructors - Never log in constructors (keep fast/side-effect free)
• Null-conditional on logger - Use logger.Method() not logger?.Method()
• Missing access modifiers - All members must have explicit modifiers
• Compiler warnings ignored - Zero tolerance for warnings
• Inline comments - Use descriptive names instead
• Using Zenject instead of VContainer
• Using MessagePipe instead of SignalBus
• Direct data access (not using Controllers)
• Memory leaks (not unsubscribing)
• Missing IDisposable implementation

🟡 Important (Should Fix)

• Missing readonly/const - Fields should be readonly/const when possible
• Hardcoded strings - Use nameof() for property/parameter names
• Using directives not in deepest scope - Method-level using when possible
• Verbose unnecessary logs - Keep only necessary logs
• Verbose code instead of LINQ
• Missing [Preserve] or [Inject] attribute
• Performance issues in hot paths
• Missing unit tests for business logic
• No XML documentation on public APIs

🟢 Nice to Have (Suggestion)

• Could use expression body
• Could use null-conditional
• Could use pattern matching
• Could improve naming
• Could simplify with modern C# features

Detailed References

C# Coding Standards

• LINQ Patterns - LINQ, extension methods, var usage
• Modern C# Features - Expression bodies, null-coalescing, pattern matching, records
• Quality & Hygiene - Nullable types, access modifiers, logging, exceptions
• Performance Optimizations - Unity patterns, LINQ performance

Unity Architecture

• VContainer DI - Complete VContainer dependency injection guide
• SignalBus Events - SignalBus event system patterns
• Data Controllers - Data Controller implementation
• Integration Patterns - Service/Bridge/Adapter for third-party SDKs
• TheOne Framework - TheOne.DI + Publisher/Subscriber alternative
• UniTask Patterns - Async/await with UniTask

Code Review

• Architecture Review - VContainer, SignalBus, Controllers violations
• C# Quality Review - LINQ, expression bodies, null handling
• Unity Specifics Review - Component access, lifecycle, cleanup
• Performance Review - Allocations, LINQ in hot paths

Summary

This skill provides comprehensive Unity development standards for TheOne Studio:

• C# Excellence: Modern, concise, professional C# code
• Unity Architecture: VContainer+SignalBus OR TheOne.DI+Publisher patterns
• Code Quality: Enforced quality, hygiene, and performance rules
• Code Review: Complete checklist for pull request reviews

Use the Quick Reference Guide above to navigate to the specific pattern you need.