unity-csharp-fundamentals

Overview

Core Unity C# patterns for safe, maintainable code. Not optimizations but fundamental practices.

Foundation Required: C# basics, Unity MonoBehaviour lifecycle

Core Topics: TryGetComponent, SerializeField, RequireComponent, Null-safe patterns, Lifecycle management

Essential Patterns

TryGetComponent (Required)

Always use TryGetComponent instead of GetComponent:

// ❌ WRONG
Rigidbody rb = GetComponent<Rigidbody>();
rb.velocity = Vector3.zero;  // NullReferenceException!

// ✅ CORRECT
Rigidbody rb;
if (TryGetComponent(out rb))
{
    rb.velocity = Vector3.zero;
}

// ✅ Cache in Awake with validation
private Rigidbody mRb;

void Awake()
{
    if (!TryGetComponent(out mRb))
    {
        Debug.LogError($"Missing Rigidbody on {gameObject.name}", this);
    }
}

Global Object Search (Unity 2023.1+)

// ❌ OBSOLETE - DON'T USE
GameManager manager = FindObjectOfType<GameManager>();

// ✅ CORRECT - Fastest (unordered)
GameManager manager = FindAnyObjectByType<GameManager>();

// ✅ CORRECT - Ordered
GameManager manager = FindFirstObjectByType<GameManager>();

// ✅ Multiple objects
Enemy[] enemies = FindObjectsByType<Enemy>(FindObjectsSortMode.None);

SerializeField Pattern

// ❌ WRONG: Public field
public float speed;

// ✅ CORRECT: SerializeField + private
[SerializeField] private float mSpeed = 5f;

// ✅ With Inspector helpers
[SerializeField, Tooltip("Units/second"), Range(0f, 100f)]
private float mMoveSpeed = 5f;

public float Speed => mSpeed;  // Read-only access

RequireComponent

[RequireComponent(typeof(Rigidbody))]
[DisallowMultipleComponent]
public class PhysicsObject : MonoBehaviour
{
    private Rigidbody mRb;

    void Awake()
    {
        TryGetComponent(out mRb);  // Guaranteed to exist
    }
}

Unity Null Safety

// ❌ WRONG: C# null operators don't work with Unity Objects
Transform target = mCached ?? FindTarget();  // Broken!
mEnemy?.TakeDamage(10);  // May fail after Destroy

// ✅ CORRECT: Explicit null check
Transform target = mCached != null ? mCached : FindTarget();

if (mEnemy != null)
{
    mEnemy.TakeDamage(10);
}

Lifecycle Order

void Awake()     { /* 1. Self-init, cache components */ }
void OnEnable()  { /* 2. Subscribe events */ }
void Start()     { /* 3. Cross-object init */ }
void OnDisable() { /* 4. Unsubscribe events */ }
void OnDestroy() { /* 5. Final cleanup */ }

Unity C# 9.0 Limitations

Important: Unity's Mono/IL2CPP runtime lacks IsExternalInit. init accessor causes compile error CS0518.

// ❌ COMPILE ERROR in Unity
public string Name { get; private init; }

// ✅ Use private set
public string Name { get; private set; }

// ✅ Or readonly field + property
private readonly string mName;
public string Name => mName;

Available: Pattern matching, switch expressions, covariant returns NOT Available: init, required (C# 11)

Quick Reference

| Pattern | Rule | |---------|------| | Component access | Always TryGetComponent, never bare GetComponent | | Serialization | [SerializeField] private, not public | | Dependencies | Use [RequireComponent] for guaranteed components | | Null checks | Explicit != null, not ?? or ?. | | Caching | Get in Awake, reuse everywhere | | Events | Subscribe in OnEnable, unsubscribe in OnDisable | | Global search | FindAnyObjectByType (fastest), not FindObjectOfType |

Reference Documentation

Component Access Patterns

• TryGetComponent variations and interface-based access
• GetComponentInChildren/Parent patterns
• Allocation-free multiple component access
• Caching strategies and performance comparisons

Attributes and Patterns

• Complete serialization attribute reference
• Inspector customization (Header, Tooltip, Range)
• Execution order control
• Conditional compilation

Language Limitations

• init accessor alternatives with code examples
• Records in Unity (limitations and workarounds)
• required modifier alternatives
• Available C# 9.0 features in Unity