📦 Lesson 6.3: Exposing Structs, Enums & Data

BlueprintType Structs

You declared USTRUCTs in Lesson 2.2. Adding BlueprintType and marking members with Blueprint access turns a struct into a type Blueprint fully understands — you can make variables of it, pass it on pins, and break/make it in graphs.

USTRUCT(BlueprintType)   // ← makes it usable as a Blueprint type
struct FWeaponStats
{
    GENERATED_BODY()

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Weapon")
    float Damage = 25.0f;

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Weapon")
    float FireRate = 5.0f;

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Weapon")
    int32 MagazineSize = 30;

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Weapon")
    FName WeaponName = TEXT("Rifle");
};

BlueprintType Enums

A UENUM(BlueprintType) becomes a dropdown in the editor and a typed pin in Blueprint. It must use enum class ... : uint8, and UMETA(DisplayName) controls the friendly labels.

UENUM(BlueprintType)
enum class EWeaponType : uint8
{
    Pistol   UMETA(DisplayName = "Pistol"),
    Rifle    UMETA(DisplayName = "Assault Rifle"),
    Shotgun  UMETA(DisplayName = "Shotgun"),
    Sniper   UMETA(DisplayName = "Sniper Rifle")
};

Now an enum property gives designers a clean dropdown:

UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Weapon")
EWeaponType Type = EWeaponType::Rifle;   // shows as a dropdown of display names

Passing Data Across

With both marked BlueprintType, they flow through UFUNCTIONs as parameters and return values — full rich data crossing the boundary.

// Return a struct to Blueprint (BlueprintPure getter):
UFUNCTION(BlueprintPure, Category = "Weapon")
FWeaponStats GetStats() const { return Stats; }

// Take a struct and an enum as parameters from Blueprint:
UFUNCTION(BlueprintCallable, Category = "Weapon")
void Configure(const FWeaponStats& NewStats, EWeaponType NewType);

// Return an array of structs — Blueprint gets a proper array of struct pins:
UFUNCTION(BlueprintCallable, Category = "Weapon")
TArray<FWeaponStats> GetAllVariants() const;

TSubclassOf Pickers

You met TSubclassOf for spawning in Lesson 3.4. As a UPROPERTY, it gives designers a filtered class picker in the editor and a class pin in Blueprint — the standard way to make "what to spawn / which type" data-driven.

// Designer picks BP_Rifle, BP_Shotgun... restricted to AWeaponBase subclasses.
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Loadout")
TSubclassOf<AWeaponBase> StartingWeaponClass;

// A whole configurable list:
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Loadout")
TArray<TSubclassOf<AWeaponBase>> UnlockableWeapons;

💡 The pattern crystallizing: a C++ system that takes TSubclassOf class references, FWeaponStats config structs, and EWeaponType enums — all set by designers in the editor — is the essence of data-driven design. The C++ provides the machinery; the data lives in Blueprint assets and the inspector. This is precisely what Lesson 6.4 assembles into the full base-class pattern, and what Module 7 formalizes with DataTables and DataAssets.

What Can Cross

A clear line on what's boundary-friendly and what isn't:

Hands-on Exercise & Quiz

UENUM(BlueprintType)
enum class ERarity : uint8 {
    Common UMETA(DisplayName="Common"), Rare UMETA(DisplayName="Rare"),
    Epic UMETA(DisplayName="Epic"), Legendary UMETA(DisplayName="Legendary")
};

USTRUCT(BlueprintType)
struct FLootEntry {
    GENERATED_BODY()
    UPROPERTY(EditAnywhere, BlueprintReadWrite) TSubclassOf<AActor> ItemClass;
    UPROPERTY(EditAnywhere, BlueprintReadWrite) ERarity Rarity = ERarity::Common;
    UPROPERTY(EditAnywhere, BlueprintReadWrite) float DropChance = 0.1f;
};

Summary

📚 Additional Resources

• Structs (Epic)
• BenUI — USTRUCT & UENUM reference

🚀 What's Next?

You now have every interop tool — functions, properties, structs, enums, class pickers. The finale of the module assembles them into the pattern: a C++ base class of mechanics, extended by Blueprint subclasses of content. One AWeaponBase, many weapons.