Unreal Engine C++ Pro

This skill provides expert-level guidelines for developing with Unreal Engine 5 using C++. It focuses on writing robust, performant, and standard-compliant code.

When to Use

Use this skill when:

• •Developing C++ code for Unreal Engine 5.x projects
• •Writing Actors, Components, or UObject-derived classes
• •Optimizing performance-critical code in Unreal Engine
• •Debugging memory leaks or garbage collection issues
• •Implementing Blueprint-exposed functionality
• •Following Epic Games' coding standards and conventions
• •Working with Unreal's reflection system (UCLASS, USTRUCT, UFUNCTION)
• •Managing asset loading and soft references

Do not use this skill when:

• •Working with Blueprint-only projects (no C++ code)
• •Developing for Unreal Engine versions prior to 5.x
• •Working on non-Unreal game engines
• •The task is unrelated to Unreal Engine development

Core Principles

1. •

   UObject & Garbage Collection:

   • •Always use UPROPERTY() for UObject* member variables to ensure they are tracked by the Garbage Collector (GC).
   • •Use TStrongObjectPtr<> if you need to keep a root reference outside of a UObject graph, but prefer addToRoot() generally.
   • •Understand the IsValid() check vs nullptr. IsValid() handles pending kill state safely.
2. •

   Unreal Reflection System:

   • •Use UCLASS(), USTRUCT(), UENUM(), UFUNCTION() to expose types to the reflection system and Blueprints.
   • •Minimize BlueprintReadWrite when possible; prefer BlueprintReadOnly for state that shouldn't be trampled by logic in UI/Level BPs.
3. •

   Performance First:

   • •Tick: Disable Ticking (bCanEverTick = false) by default. Only enable it if absolutely necessary. Prefer timers (GetWorldTimerManager()) or event-driven logic.
   • •Casting: Avoid Cast<T>() in hot loops. Cache references in BeginPlay.
   • •Structs vs Classes: Use F structs for data-heavy, non-UObject types to reduce overhead.

Naming Conventions (Strict)

Follow Epic Games' coding standard:

• •Templates: Prefix with T (e.g., TArray, TMap).
• •UObject: Prefix with U (e.g., UCharacterMovementComponent).
• •AActor: Prefix with A (e.g., AMyGameMode).
• •SWidget: Prefix with S (Slate widgets).
• •Structs: Prefix with F (e.g., FVector).
• •Enums: Prefix with E (e.g., EWeaponState).
• •Interfaces: Prefix with I (e.g., IInteractable).
• •Booleans: Prefix with b (e.g., bIsDead).

Common Patterns

1. Robust Component Lookup

Avoid GetComponentByClass in Tick. Do it in PostInitializeComponents or BeginPlay.

void AMyCharacter::PostInitializeComponents() {
    Super::PostInitializeComponents();
    HealthComp = FindComponentByClass<UHealthComponent>();
    check(HealthComp); // Fail hard in dev if missing
}

2. Interface Implementation

Use interfaces to decouple systems (e.g., Interaction system).

// Interface call check
if (TargetActor->Implements<UInteractable>()) {
    IInteractable::Execute_OnInteract(TargetActor, this);
}

3. Async Loading (Soft References)

Avoid hard references (UPROPERTY(EditDefaultsOnly) TSubclassOf<AActor>) for massive assets which force load orders. Use TSoftClassPtr or TSoftObjectPtr.

UPROPERTY(EditAnywhere, BlueprintReadWrite)
TSoftClassPtr<AWeapon> WeaponClassToLoad;

void AMyCharacter::Equip() {
    if (WeaponClassToLoad.IsPending()) {
        WeaponClassToLoad.LoadSynchronous(); // Or use StreamableManager for async
    }
}

Debugging

• •Logging: Use UE_LOG with custom categories.
  cpp

  DEFINE_LOG_CATEGORY_STATIC(LogMyGame, Log, All);
  UE_LOG(LogMyGame, Warning, TEXT("Health is low: %f"), CurrentHealth);
  

• •Screen Messages:
  cpp

  if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("Died!"));
  

• •Visual Logger: extremely useful for AI debugging. Implement IVisualLoggerDebugSnapshotInterface.

Checklist before PR

• • Does this Actor need to Tick? Can it be a Timer?
• • Are all UObject* members wrapped in UPROPERTY?
• • Are hard references (TSubclassOf) causing load chains? Can they be Soft Ptrs?
• • Did you clean up verified delegates in EndPlay?