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Syntax and C++ Basics

This page covers the C++ features Unity developers usually run into first when reading Unreal code.

Header and Source Files

Unity Version

In Unity, a class often lives in one .cs file.

Unreal Version

In Unreal C++, a class usually has:

  • a header file such as MyActor.h
  • a source file such as MyActor.cpp

The header declares the class. The source file defines the function bodies.

Key Difference

You usually split declarations and implementations. That is standard C++, and it affects includes, compile times, and generated code.

Example

Unity C

public class Health : MonoBehaviour
{
    public int currentHealth = 100;

    public void TakeDamage(int amount)
    {
        currentHealth -= amount;
    }
}

Unreal C++

// HealthActor.h
#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "HealthActor.generated.h"

UCLASS()
class MYGAME_API AHealthActor : public AActor
{
    GENERATED_BODY()

public:
    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Health")
    int32 CurrentHealth = 100;

    UFUNCTION(BlueprintCallable, Category = "Health")
    void TakeDamageAmount(int32 Amount);
};

// HealthActor.cpp
#include "HealthActor.h"

void AHealthActor::TakeDamageAmount(int32 Amount)
{
    CurrentHealth -= Amount;
}

Important Syntax

Syntax Meaning Why You See It in Unreal
#include Includes declarations from another header Unreal code still follows C++ include rules.
:: Scope resolution Used for class functions, namespaces, and static members.
-> Access a member through a pointer Common because many engine APIs return pointers.
* Pointer declaration or dereference Unreal uses pointers heavily for UObject references.
& Reference or address-of operator Used for output parameters and pass-by-reference.
const Says a value or method should not modify data Common in Unreal APIs and function parameters.
auto Let the compiler infer the type Useful when the type is obvious from the right side.
nullptr Null pointer literal Use this instead of NULL or 0.
TEXT("...") Wraps string literals for Unreal character encoding expectations Common with logging and FString construction.

Variables

Unity C# Unreal C++
float speed = 5f; float Speed = 5.0f;

Unity C

float speed = 5f;
bool isAlive = true;

Unreal C++

float Speed = 5.0f;
bool bIsAlive = true;

Unreal commonly prefixes booleans with b, such as bIsAlive.

Functions

Unity C# Unreal C++
void JumpNow() void JumpNow(); in the header, then define it in .cpp

Unity C

void JumpNow()
{
    Debug.Log("Jump");
}

Unreal C++

void AMyCharacter::JumpNow()
{
    UE_LOG(LogTemp, Log, TEXT("Jump"));
}

Classes

Unity C# Unreal C++
public class Mover : MonoBehaviour class AMyMover : public AActor

Unity C

public class Mover : MonoBehaviour
{
}

Unreal C++

UCLASS()
class MYGAME_API AMyMover : public AActor
{
    GENERATED_BODY()
};

Null Checks

Unity C# Unreal C++
if (target != null) if (Target != nullptr)

Unity C

if (target != null)
{
    target.SetActive(true);
}

Unreal C++

if (Target != nullptr)
{
    Target->SetActorHiddenInGame(false);
}

Logging

Unity C# Unreal C++
Debug.Log("Hello"); UE_LOG(LogTemp, Log, TEXT("Hello"));

Unity C

Debug.Log("Hello, Unity!");

Unreal C++

UE_LOG(LogTemp, Log, TEXT("Hello, Unreal!"));

const and References

Pass larger structs by const reference when you do not need to copy them.

void SetSpawnPoint(const FVector& NewLocation);

This means:

  • do not copy the FVector
  • do not modify NewLocation inside the function

auto

auto is useful when the type is obvious or long.

auto* World = GetWorld();
auto Location = GetActorLocation();

Do not overuse it when the type would become unclear to a beginner.

Unreal Naming Conventions

Pattern Example Meaning
A prefix AActor Actor-derived class
U prefix UObject, UActorComponent UObject-derived class
F prefix FVector, FText Struct or value type
E prefix EInputEvent Enum
T prefix TArray, TMap Template type
b prefix bIsVisible Boolean

Common Mistake

A common trap is writing a wrapper method with the same name as an engine method, such as SetActorLocation, then accidentally calling itself and causing recursion. Use a clearer name like MoveToLocation if you are adding your own helper.