1. TObjectPtr
Unreal Engine GC-safe Pointer Wrapper for Unreal UObjects. More safer, little slower(small indirection) than T*
- Use
UPROPERTY + TObjectPtrfor class/struct members that must be tracked by GC - Use
T*for locals, function params/returns, temporary variables
2. TMap<K, V>, TInstnacedStruct, UDataAAsset
- TMap: Hashmap implementation for Unreal Engine.
- TInstancedStruct: If I make a Struct in Unreal Engine, we can’t see it in Unreal Editor because Struct is not a UObject. TInstancedStruct wraps our Struct to make a UObject, which we can see and modify in our UE Editor.
- UDataAsset: The dataclass of Unreal Engine. Good for storing static data that will be used in the game.
/**
* Defines All the types of Interactions in IRL Mode.
* These interactions are stored in IRL Actors and are activated when the player presses "Interact" Button to the actor.
*/
USTRUCT(BlueprintType)
struct FIRLInteraction
{
GENERATED_BODY()
UPROPERTY(EditAnywhere, BlueprintReadWrite)
FName Id;
UPROPERTY(EditAnywhere, BlueprintReadWrite)
FString Text;
UPROPERTY(EditAnywhere, BlueprintReadWrite, meta=(GetOptions="GetInteractionIds"))
FName NextId;
};
/**
* The most common interaction: text conversations. Made in nodes, where each node is one unit of text(in one screen)
*/
USTRUCT(BlueprintType)
struct FConversation: public FIRLInteraction
{
GENERATED_BODY()
UPROPERTY(EditAnywhere, BlueprintReadWrite)
FString CharacterName;
};
// Usage ex)
#pragma once
#include "CoreMinimal.h"
#include "GameplayTagContainer.h"
#include "IRLInteractions.h"
#include "Engine/DataAsset.h"
#include "StructUtils/InstancedStruct.h"
#include "IRLInteractionDatabase.generated.h"
/**
* Defines the interaction event of one actor in different parts of the story.
*/
UCLASS()
class RACETOWORLDFIRST1_API UIRLInteractionDatabase : public UDataAsset
{
GENERATED_BODY()
public:
UPROPERTY(EditAnywhere)
TMap<FName, TInstancedStruct<FIRLInteraction>> AllInteractionsDatabase;
TMap<FGameplayTag, TInstancedStruct<FIRLInteraction>> InteractionInEachLevel;
UFUNCTION()
TArray<FName> GetInteractionIds() const
{
TArray<FName> Out;
Out.Add(NAME_None);
for (const TPair<FName, TInstancedStruct<FIRLInteraction>>& Item: AllInteractionsDatabase)
{
const FName& Key = Item.Key;
if (!Key.IsNone())
{
Out.Add(Key);
}
}
Out.Sort(FNameLexicalLess());
return Out;
}
const FIRLInteraction* GetInteraction(const FGameplayTag& CurrentLevel) const
{
const TInstancedStruct<FIRLInteraction>* InteractionStruct = InteractionInEachLevel.Find(CurrentLevel);
if (!InteractionStruct)
{
return nullptr;
}
const FIRLInteraction* Interaction = InteractionStruct->GetPtr();
if (!Interaction)
{
return nullptr;
}
if (Interaction->Id.IsNone())
{
return nullptr;
}
return Interaction;
}
};
3. Check if A is Subclass of T
// simple version
if (Obj && Obj->IsA(T::StaticClass())) { ... }
// more versatile version using assing
if (T* AsT = Cast<T>(Obj))
4. UGameplayStatics
Contains all the useful utilities for managing a game, such as having all instances of a class, loading new levels, etc
#include "Kismet/GameplayStatics.h"
// From inside an Actor/Component:
UGameplayStatics::OpenLevel(this, FName("Ch1_Scene2")); // uses 'this' to get UWorld
TArray<AActor*> Found;
UGameplayStatics::GetAllActorsOfClass(this, AEnemy::StaticClass(), Found);
// Direct UWorld alternative:
GetWorld()->SpawnActor<AMyActor>(Class, Transform);
- Unreal Game Hierarchy
- GameInstance: Global across entire App.
- World: Has multiple levels,
- Persistent Level: The root level that always exists in the world.
- World Partition: Replaces Streaming levels in UE5. Divides world into grid of streamed cells and loads/unloads them dynamically(ex) in Runescape, where the map is dynamically updated as we get out of the current loaded map)
- Level: “Set of Actors”