UBlueprintFunctionLibrary class in Unreal Engine

A base class for any function libraries exposed to blueprints. It is also useful for working with data, files and other properties right in the Editor mode.

Vladimír NeporAuthorVladimír Nepor
Published

UBlueprintFunctionLibrary is a very usefull Class when there's a need to e.g. work with data and files right in editor (for their preparation and simpliefied development), without need to switch to runtime.

Creating assets with C++ & UBlueprintFunctionLibrary

#include "Kismet/BlueprintFunctionLibrary.h" // Engine
UCLASS()
class UExampleClass : public <mark>UBlueprintFunctionLibrary</mark>
{
 GENERATED_BODY()

public:
/**
 * Editor Only - Will not work in packaged build.
 *
 * Create an asset.
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param AssetClass	The class of the asset to create
 * @param AssetFactory	Optional. The factory to use to create the asset
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
UFUNCTION(BlueprintCallable, Category = " ... ")
<strong>static UObject* CreateAsset(FString AssetPath, UClass* AssetClass, class UFactory* AssetFactory, bool& bOutSuccess, FString& OutInfoMsg);</strong>
}

.cpp file - CreateAsset function

#include "AssetToolsModule.h" // <mark>AssetTools (Editor Only)*</mark>

UObject* UExampleClass::CreateAsset(FString AssetPath, UClass* AssetClass, UFactory* AssetFactory, bool& bOutSuccess, FString& OutInfoMsg)
{
 // Get the asset tools module
 IAssetTools& AssetTools = FModuleManager::GetModuleChecked&lt;FAssetToolsModule&gt;("AssetTools").Get();

 // Find right factory
 UFactory* Factory = AssetFactory;
 if (Factory == nullptr)
 { 
   for (UFactory* Fac : AssetTools.GetNewAssetFactories())
   {
      if (Fac-&gt;SupportedClass == AssetClass)
      {
         Factory = Fac;
         break;
      }
   }

   if (Factory == nullptr)
   {
     bOutSuccess = false;
     OutInfoMsg = FString::Printf(TEXT("Create Asset Failed - Was not able to find factory for AssetClass. '%s'"), *AssetPath);
     return nullptr;
   }
 }

 // Can factory create the desired asset?
 if (Factory-&gt;SupportedClass != AssetClass)
 {
   bOutSuccess = false;
   OutInfoMsg = FString::Printf(TEXT("Create Asset Failed - Factory cannot create desired AssetClass. '%s'"), *AssetPath);
   return nullptr;
 }

 <mark>// Create asset
 UObject* Asset = AssetTools.CreateAsset(FPaths::GetBaseFilename(AssetPath), FPaths::GetPath(AssetPath), AssetClass, Factory);</mark>

  // Make sure it worked
  if (Asset == nullptr)
  {
    bOutSuccess = false;
    OutInfoMsg = FString::Printf(TEXT("Create Asset Failed - Either the path is invalid or the asset already exists. '%s'"), *AssetPath);
    return nullptr;
  }

  // Return the asset
  bOutSuccess = true;
  OutInfoMsg = FString::Printf(TEXT("Create Asset Succeeded - '%s'"), *AssetPath);
  <strong>return Asset;</strong>
}

* As of AssetToolsModule.h is AssetTools type of dependency, that is not attached to the project by default, it must be added to .Build.cs file manually.

PrivateDependencyModuleNames.AddRange
(
 new string[]
  { 
   // Default Modules
   "Core", 
   "CoreUObject", 
   "Engine", 
   // New Modules - Editor Only
   <mark>"AssetTools"</mark>,
  }
);

Creating various kind of assets

  • World asset

    #include "Engine/World.h" // Engine
#include "Factories/WorldFactory.h" // <strong>"UnrealEd" (Editor Only) - dependency must be added to .Build.cs file</strong>
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a World asset.</mark>
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
UWorld* UExampleClass::<strong>CreateWorldAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  // Factory
  UWorldFactory* Factory = NewObject&lt;<a href="https://dev.epicgames.com/documentation/en-us/unreal-engine/API/Editor/UnrealEd/UWorldFactory" target="_blank">UWorldFactory</a>&gt;();
  Factory-&gt;bInformEngineOfWorld = false;
  Factory-&gt;bCreateWorldPartition = false;
  Factory-&gt;FeatureLevel = ERHIFeatureLevel::ES3_1;

  // Create and return asset
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, UWorld::StaticClass(), Factory, bOutSuccess, OutInfoMsg);
  return Cast&lt;UWorld&gt;(Asset);
}

  • Material asset

    #include "Materials/Material.h" // Engine
#include "Factories/MaterialFactoryNew.h" //<strong>"UnrealEd" (Editor Only) - dependency must be added to .Build.cs file</strong>
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a Material asset.</mark>
 *
 * @param AssetPath		The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
*/
UMaterial* UExampleClass::<strong>CreateMaterialAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  // Factory
  UMaterialFactoryNew* Factory = NewObject&lt;<a href="https://dev.epicgames.com/documentation/en-us/unreal-engine/API/Editor/UnrealEd/UMaterialFactoryNew" target="_blank">UMaterialFactoryNew</a>&gt;();
  Factory-&gt;InitialTexture = nullptr;

  // Create and return asset
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, UMaterial::StaticClass(), Factory, bOutSuccess, OutInfoMsg);
  return Cast&lt;UMaterial&gt;(Asset);
}

  • LevelSequence asset

    #include "LevelSequence.h" // <strong>"LevelSequence" - dependency must be added to .Build.cs file</strong>
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a LevelSequence asset.</mark>
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
ULevelSequence* UExampleClass::<strong>CreateLevelSequenceAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, ULevelSequence::StaticClass(), nullptr, bOutSuccess, OutInfoMsg);
  return Cast&lt;ULevelSequence&gt;(Asset);
}

  • NiagaraSystem asset

    #include "NiagaraSystem.h" // <strong>"Niagara" - dependency must be added to .Build.cs file</strong>
#include "BehaviorTree/BlackboardData.h"
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a NiagaraSystem asset.</mark>
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
UNiagaraSystem* UExampleClass::<strong>CreateNiagaraSystemAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, UBlackboardData::StaticClass(), nullptr, bOutSuccess, OutInfoMsg);
  return Cast&lt;UNiagaraSystem&gt;(Asset);
}

  • SoundCue asset

    #include "Sound/SoundCue.h" // Engine
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a SoundCue asset.</mark>
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
USoundCue* UExampleClass::<strong>CreateSoundCueAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, USoundCue::StaticClass(), nullptr, bOutSuccess, OutInfoMsg);
  return Cast&lt;USoundCue&gt;(Asset);
}

  • Enum asset

    #include "Engine/UserDefinedEnum.h" // Engine
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a Enum asset.</mark>
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
UUserDefinedEnum* UExampleClass::<strong>CreateEnumAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, UUserDefinedEnum::StaticClass(), nullptr, bOutSuccess, OutInfoMsg);
  return Cast&lt;UUserDefinedEnum&gt;(Asset);
}

  • Struct asset

    #include "Engine/UserDefinedStruct.h" // Engine
/**
 * Editor Only - Will not work in packaged build.
 *
 * <mark>Create a Struct asset.</mark>
 *
 * @param AssetPath	The path of where to create the asset: "/Game/Folder/MyAsset"
 * @param bOutSuccess	If the action was a success or not
 * @param OutInfoMsg	More information about the action's result
 *
 * @return The created asset
 */
UUserDefinedStruct* UExampleClass::<strong>CreateStructAsset(FString AssetPath, bool& bOutSuccess, FString& OutInfoMsg)</strong>
{
  UObject* Asset = <a href="#create-asset">CreateAsset</a>(AssetPath, UUserDefinedStruct::StaticClass(), nullptr, bOutSuccess, OutInfoMsg);
  return Cast&lt;UUserDefinedStruct&gt;(Asset);
}

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