UAssetDefinition

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Asset Definitions represent top level assets that are known to the editor.

Conversion Guide Asset Definitions (UAssetDefinitionDefault) are a replacement to the Asset Actions (FAssetTypeActions_Base) system. The reasons for the replacement are multitude, but the highlights are,

Asset Definitions no longer do things like provide a GetActions function, the replacement for this is you using the new UToolMenu extension system to register actions for the assets, an example is in this document. A lot of the APIs have been tweaked and cleaned up to make them easier to upgrade in the future, a lot of the original API for Asset Actions were added one at a time, and several of them could be combined in simpler ways. Another benefit is soon we might be able to make the AssetTools module no longer a circular dependency.

All of this is in service to what was previously impossible. To be able to right click on assets in the Content Browser and NOT have the asset and every asset it knew about load on right click, this previous impossible to escape byproduct slowed down working in the editor constantly because things that didn’t require opening the asset became necessary, and some assets could load A LOT of other content.

Unfortunately I can’t prevent people from backsliding, at least for now. Even after fixing the APIs to not require loading, people need to be cleverer (Use Asset Tag Data) in how they provide right click options for assets. But to help, you can run the editor with -WarnIfAssetsLoaded on the command line. I’ve added a new utility class to the engine called, FWarnIfAssetsLoadedInScope, it causes notifications with callstacks to be popped up telling you what code is actually responsible for any asset loads within earmarked scopes that should NOT be loading assets.

Backwards Compatibility The new system is fully* backwards compatible. Asset Definitions are registered with the old Asset Tools (IAssetTools::RegisterAssetTypeActions) this is done through the FAssetDefinitionProxy. Similarly, Asset Actions (FAssetTypeActions_Base) are registered with the Asset Definition Registry with an Asset Definition Proxy (UAssetDefinition_AssetTypeActionsProxy).

When converting Asset Actions to AssetDefinitions and you’re trying to understand how to map a specific function to the new system it can be helpful to look at the equivalent function in FAssetDefinitionProxy.

IMPORTANT - You are no longer allowed to register multiple Asset Definitions for the same Asset Class. There were a very small number of people doing this to do some tricky things with filters which are no longer required. The new system will yell at you if you do this.

Registration Registering your Asset Definition is no longer required like it was for Asset Actions. The UObjects are automatically registered with the new Asset Definition Registry (UAssetDefinitionRegistry).

You no longer need to register Categories for your Asset Definition, like you had to do with Asset Actions. Your Assets categories are just an array of FAssetCategoryPath. They have accelerator constructors to just take an FText for the main category, and the sub category (if there is one) which replaces the whole “GetSubMenus” function from Asset Actions. The new version can go further, with multiple sub menus and categories, but the UI isn’t set up for it yet.

GetActions The function GetActions no longer exists, the replacement is to somewhere put a self registering callback to register the UToolMenu extension, but you can just put it at the bottom of your .cpp for your AssetDefinition, that is where the others are. The template goes something like this,

// Menu Extensions //-----------------------------------------------------------------

namespace MenuExtension_YOUR_CLASS_TYPE { static void ExecuteActionForYourType(const FToolMenuContext& InContext) { const UContentBrowserAssetContextMenuContext* Context = UContentBrowserAssetContextMenuContext::FindContextWithAssets(InContext);

for (YOUR_CLASS_TYPE* LoadedInstance : Context->LoadSelectedObjects()) { } }

static FDelayedAutoRegisterHelper DelayedAutoRegister(EDelayedRegisterRunPhase::EndOfEngineInit, []{ UToolMenus::RegisterStartupCallback(FSimpleMulticastDelegate::FDelegate::CreateLambda([]() { FToolMenuOwnerScoped OwnerScoped(UE_MODULE_NAME); UToolMenu* Menu = UE::ContentBrowser::ExtendToolMenu_AssetContextMenu(YOUR_CLASS_TYPE::StaticClass());

FToolMenuSection& Section = Menu->FindOrAddSection("GetAssetActions"); Section.AddDynamicEntry(NAME_None, FNewToolMenuSectionDelegate::CreateLambda(FToolMenuSection& InSection { const TAttribute Label = LOCTEXT("YOUR_ASSET_TYPE_ExecuteActionForYourType", "Execute Action For Your Type"); const TAttribute ToolTip = LOCTEXT("YOUR_ASSET_TYPE_ExecuteActionForYourTypeTooltip", "This will execute the action for your type."); const FSlateIcon Icon = FSlateIcon();

FToolUIAction UIAction; UIAction.ExecuteAction = FToolMenuExecuteAction::CreateStatic(&ExecuteActionForYourType); InSection.AddMenuEntry("YOUR_ASSET_TYPE_ExecuteActionForYourType", Label, ToolTip, Icon, UIAction); )); })); }); }

It’s very important that you do not load the asset in your CanExecuteAction callback or in this self callback, you should save that until you finally get Executed. If you’re looking for examples, there are tons you'll find by searching for “namespace MenuExtension_”.

GetFilterName & BuildBackendFilter These functions have been replaced by BuildFilters. The new function is great, you can provide an array of filters that are available with this asset. So for example, Blueprints provide a filter for Blueprint Class, but they also provide the filters for Blueprint Interface, Blueprint Macro Library and Blueprint Function library, which are all UBlueprint assets, but differ based on Asset Tag data.

Syntax

UCLASS (MinimalAPI, Abstract)  
class UAssetDefinition : public UObject  
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UCLASS (MinimalAPI, Abstract) class UAssetDefinition : public UObject

Inheritance Hierarchy

• UObjectBase → UObjectBaseUtility → UObject → UAssetDefinition

Derived Classes

• UAssetDefinitionDefault

Constructors

Variables

Protected

Functions

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Public Virtual

Overridden from UObject

Protected Virtual