unreal-engine-cpp-pro

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English

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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.

本 skill 提供了使用 C++ 进行 Unreal Engine 5 开发的专家级指南，重点是编写稳健、高性能且符合标准的代码。

When to Use

何时使用

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

在以下情况下使用本 skill：

为 Unreal Engine 5.x 项目开发 C++ 代码
编写 Actor、Component 或派生自 UObject 的类
优化 Unreal Engine 中对性能至关重要的代码
调试内存泄漏或垃圾回收问题
实现向 Blueprint 暴露的功能
遵循 Epic Games 的编码标准与约定
使用 Unreal 的反射系统（UCLASS、USTRUCT、UFUNCTION）
管理资产加载和软引用

在以下情况下不要使用本 skill：

处理仅使用 Blueprint 的项目（无 C++ 代码）
开发 Unreal Engine 5.x 之前的版本
使用非 Unreal 游戏引擎进行开发
任务与 Unreal Engine 开发无关

Core Principles

核心原则

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.
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.
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.

UObject 与垃圾回收：
- 对
```
UObject*
```
  成员变量始终使用
```
UPROPERTY()
```
  ，以确保垃圾回收器（GC）能够跟踪它们。
- 如果需要在 UObject 对象图之外保留根引用，请使用
```
TStrongObjectPtr<>
```
  ；但通常更推荐使用
```
addToRoot()
```
  。
- 理解
```
IsValid()
```
  检查与
```
nullptr
```
  检查之间的区别。
```
IsValid()
```
  能够安全处理 pending kill 状态。
Unreal 反射系统：
- 使用
```
UCLASS()
```
  、
```
USTRUCT()
```
  、
```
UENUM()
```
  、
```
UFUNCTION()
```
  将类型暴露给反射系统和 Blueprint。
- 尽可能减少
```
BlueprintReadWrite
```
  的使用；对于不应被 UI/Level BPs 中的逻辑覆盖的状态，优先使用
```
BlueprintReadOnly
```
  。
性能优先：
- Tick：默认禁用 Tick（
```
bCanEverTick = false
```
  ）。仅在绝对必要时启用。优先使用计时器（
```
GetWorldTimerManager()
```
  ）或事件驱动逻辑。
- Casting：避免在热循环中调用
```
Cast<T>()
```
  。在
```
BeginPlay
```
  中缓存引用。
- 结构体与类：对于数据密集型的非 UObject 类型，使用
```
F
```
  结构体以降低开销。

Naming Conventions (Strict)

命名约定（严格）

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
```
).

遵循 Epic Games 的编码标准：

模板：使用
```
T
```
作为前缀（例如
```
TArray
```
、
```
TMap
```
）。
UObject：使用
```
U
```
作为前缀（例如
```
UCharacterMovementComponent
```
）。
AActor：使用
```
A
```
作为前缀（例如
```
AMyGameMode
```
）。
SWidget：使用
```
S
```
作为前缀（Slate 控件）。
结构体：使用
```
F
```
作为前缀（例如
```
FVector
```
）。
枚举：使用
```
E
```
作为前缀（例如
```
EWeaponState
```
）。
接口：使用
```
I
```
作为前缀（例如
```
IInteractable
```
）。
布尔值：使用
```
b
```
作为前缀（例如
```
bIsDead
```
）。

Common Patterns

常见模式

1. Robust Component Lookup

1. 健壮的组件查找

Avoid

GetComponentByClass

Tick

. Do it in

PostInitializeComponents

BeginPlay

cpp

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

避免在

Tick

中调用

GetComponentByClass

。应在

PostInitializeComponents

或

BeginPlay

中执行。

cpp

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

2. Interface Implementation

2. 接口实现

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

cpp

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

使用接口解耦系统（例如交互系统）。

cpp

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

3. Async Loading (Soft References)

3. 异步加载（软引用）

Avoid hard references (

UPROPERTY(EditDefaultsOnly) TSubclassOf<AActor>

) for massive assets which force load orders. Use

TSoftClassPtr

TSoftObjectPtr

cpp

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

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

避免对大型资产使用硬引用（

UPROPERTY(EditDefaultsOnly) TSubclassOf<AActor>

），因为硬引用会强制决定加载顺序。请使用

TSoftClassPtr

或

TSoftObjectPtr

。

cpp

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

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

Debugging

调试

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
```
.

日志记录：使用

UE_LOG

并定义自定义日志类别。

cpp

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

屏幕消息：

cpp

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

Visual Logger：对 AI 调试极为有用。实现
```
IVisualLoggerDebugSnapshotInterface
```
。

Checklist before PR

PR 前检查清单

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
```
?

这个 Actor 是否需要 Tick？能否改用 Timer？
是否所有
```
UObject*
```
成员都使用了
```
UPROPERTY
```
包裹？
硬引用（TSubclassOf）是否造成了加载链？能否改为 Soft Ptr？
是否已在
```
EndPlay
```
中清理并核验委托？

Limitations

限制

Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

仅当任务明确符合上述范围时使用本 skill。
不要将输出视为替代针对具体环境的验证、测试或专家评审的手段。
如果缺少必要的输入、权限、安全边界或成功标准，请停止操作并请求澄清。