95 lines
3.7 KiB
Markdown
95 lines
3.7 KiB
Markdown
---
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name: unreal-engine-cpp-pro
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description: Expert guide for Unreal Engine 5.x C++ development, covering UObject hygiene, performance patterns, and best practices.
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---
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# Unreal Engine C++ Pro
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This skill provides expert-level guidelines for developing with Unreal Engine 5 using C++. It focuses on writing robust, performant, and standard-compliant code.
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## Core Principles
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1. **UObject & Garbage Collection**:
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* Always use `UPROPERTY()` for `UObject*` member variables to ensure they are tracked by the Garbage Collector (GC).
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* Use `TStrongObjectPtr<>` if you need to keep a root reference outside of a UObject graph, but prefer `addToRoot()` generally.
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* Understand the `IsValid()` check vs `nullptr`. `IsValid()` handles pending kill state safely.
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2. **Unreal Reflection System**:
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* Use `UCLASS()`, `USTRUCT()`, `UENUM()`, `UFUNCTION()` to expose types to the reflection system and Blueprints.
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* Minimize `BlueprintReadWrite` when possible; prefer `BlueprintReadOnly` for state that shouldn't be trampled by logic in UI/Level BPs.
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3. **Performance First**:
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* **Tick**: Disable Ticking (`bCanEverTick = false`) by default. Only enable it if absolutely necessary. Prefer timers (`GetWorldTimerManager()`) or event-driven logic.
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* **Casting**: Avoid `Cast<T>()` in hot loops. Cache references in `BeginPlay`.
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* **Structs vs Classes**: Use `F` structs for data-heavy, non-UObject types to reduce overhead.
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## Naming Conventions (Strict)
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Follow Epic Games' coding standard:
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* **Templates**: Prefix with `T` (e.g., `TArray`, `TMap`).
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* **UObject**: Prefix with `U` (e.g., `UCharacterMovementComponent`).
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* **AActor**: Prefix with `A` (e.g., `AMyGameMode`).
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* **SWidget**: Prefix with `S` (Slate widgets).
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* **Structs**: Prefix with `F` (e.g., `FVector`).
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* **Enums**: Prefix with `E` (e.g., `EWeaponState`).
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* **Interfaces**: Prefix with `I` (e.g., `IInteractable`).
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* **Booleans**: Prefix with `b` (e.g., `bIsDead`).
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## Common Patterns
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### 1. Robust Component Lookup
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Avoid `GetComponentByClass` in `Tick`. Do it in `PostInitializeComponents` or `BeginPlay`.
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```cpp
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void AMyCharacter::PostInitializeComponents() {
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Super::PostInitializeComponents();
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HealthComp = FindComponentByClass<UHealthComponent>();
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check(HealthComp); // Fail hard in dev if missing
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}
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```
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### 2. Interface Implementation
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Use interfaces to decouple systems (e.g., Interaction system).
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```cpp
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// Interface call check
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if (TargetActor->Implements<UInteractable>()) {
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IInteractable::Execute_OnInteract(TargetActor, this);
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}
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```
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### 3. Async Loading (Soft References)
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Avoid hard references (`UPROPERTY(EditDefaultsOnly) TSubclassOf<AActor>`) for massive assets which force load orders. Use `TSoftClassPtr` or `TSoftObjectPtr`.
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```cpp
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UPROPERTY(EditAnywhere, BlueprintReadWrite)
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TSoftClassPtr<AWeapon> WeaponClassToLoad;
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void AMyCharacter::Equip() {
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if (WeaponClassToLoad.IsPending()) {
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WeaponClassToLoad.LoadSynchronous(); // Or use StreamableManager for async
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}
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}
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```
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## Debugging
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* **Logging**: Use `UE_LOG` with custom categories.
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```cpp
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DEFINE_LOG_CATEGORY_STATIC(LogMyGame, Log, All);
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UE_LOG(LogMyGame, Warning, TEXT("Health is low: %f"), CurrentHealth);
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```
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* **Screen Messages**:
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```cpp
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if (GEngine) GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("Died!"));
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```
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* **Visual Logger**: extremely useful for AI debugging. Implement `IVisualLoggerDebugSnapshotInterface`.
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## Checklist before PR
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- [ ] Does this Actor need to Tick? Can it be a Timer?
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- [ ] Are all `UObject*` members wrapped in `UPROPERTY`?
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- [ ] Are hard references (TSubclassOf) causing load chains? Can they be Soft Ptrs?
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- [ ] Did you clean up verified delegates in `EndPlay`?
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