vault backup: 2024-10-12 17:19:45

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Object/IncludeAssetBundles/IncludeAssetBundles.md

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+# IncludeAssetBundles
+
+- **功能描述：** 用于UPrimaryDataAsset的子对象属性，指定应该继续递归到该子对象里去探测AssetBundle数据。
+- **使用位置：** UPROPERTY
+- **引擎模块：** Object Property
+- **元数据类型：** string="abc"
+- **限制类型：** UPrimaryDataAsset内部的ObjectPtr属性
+- **关联项：** [AssetBundles](../AssetBundles/AssetBundles.md)
+- **常用程度：** ★★
+
+用于UPrimaryDataAsset的子对象属性，指定应该继续递归到该子对象里去探测AssetBundle数据。
+
+这样这些指对象内部的 FSoftObjectPtr 或 FSoftObjectPath 属性，其上面标明的AssetBundle的数据才会被解析添加到UPrimaryDataAsset的AssetBundleData里。
+
+- 默认情况下，InitializeAssetBundlesFromMetadata_Recursive只会分析到UPrimaryDataAsset的本身这一层级的属性，比如下面的Icon和Mesh属性。
+- 而如果再嵌套了一层，就是UPrimaryDataAsset下面拥有只对象，UMyProperty_Asset_ChildObject，而UMyProperty_Asset_ChildObject 里面又包含FSoftObjectPath ，希望它被属于AssetBundles 的一部分，在加载UPrimaryDataAsset的时候同时一并加载。这个时候就需要告诉引擎需要继续分析这个子对象。
+- 注意到UMyProperty_Asset_ChildObject我都是用TObjectPtr，是个硬引用，该对象在UMyProperty_Asset_Item 被加载的时候也会自然被加载进来。因此无论如何，UMyProperty_Asset_ChildObject 都会被加载进来。但是UMyProperty_Asset_ChildObject 内部的ChildIcon是用TSoftObjectPtr，是软引用，因此必须依赖AssetBundle的机制才会被加载。
+
+## 测试代码：
+
+```cpp
+UCLASS(BlueprintType)
+class INSIDER_API UMyProperty_Asset_ChildObject :public UDataAsset
+{
+	GENERATED_BODY()
+public:
+	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (AssetBundles = "Client"))
+	TSoftObjectPtr<UTexture2D> ChildIcon;
+};
+
+UCLASS(BlueprintType)
+class INSIDER_API UMyProperty_Asset_Item :public UPrimaryDataAsset
+{
+	GENERATED_BODY()
+public:
+	UPROPERTY(BlueprintReadWrite, EditAnywhere)
+	FString Name;
+	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (AssetBundles = "UI,Game"))
+	TSoftObjectPtr<UTexture2D> Icon;
+	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (AssetBundles = "Game"))
+	TSoftObjectPtr<UStaticMesh> Mesh;
+
+public:
+	UPROPERTY(BlueprintReadWrite, EditAnywhere)
+	TObjectPtr<UMyProperty_Asset_ChildObject> MyChildObject_NotIncludeAssetBundles;
+
+	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (IncludeAssetBundles))
+	TObjectPtr<UMyProperty_Asset_ChildObject> MyChildObject_IncludeAssetBundles;
+public:
+	virtual FPrimaryAssetId GetPrimaryAssetId() const override;
+};
+```
+
+## 测试效果：
+
+配置的数据图的下部分，分别配置了两张图片。但在LoadPrimaryAsset后，只有MyChildObject_IncludeAssetBundles内部的ChildIcon才被加载进来。
+
+![IncludeAssetBundles](IncludeAssetBundles.jpg)
+
+如果分析UMyProperty_Asset_Item 的AssetBunbleData数据，会发现其Client只包含第二张Stone图片的路径。这是因为只有第二张图片才被分析到并包含进来。
+
+```cpp
+{
+				BundleName = "Client";
+				BundleAssets =
+				{
+					{
+						AssetPath =
+						{
+							PackageName = "/Game/Asset/Image/T_Shop_Stone";
+							AssetName = "T_Shop_Stone";
+						};
+						SubPathString = "";
+					};
+				},
+				AssetPaths =
+				{
+					{
+						PackageName = "/Game/Asset/Image/T_Shop_Stone";
+						AssetName = "T_Shop_Stone";
+					};
+				},
+			};
+```
+
+## 原理：
+
+UPrimaryDataAsset下的属性如果是个Object属性，只当有IncludeAssetBundles的时候，才会进一步递归向下探测。
+
+```cpp
+void UAssetManager::InitializeAssetBundlesFromMetadata_Recursive(const UStruct* Struct, const void* StructValue, FAssetBundleData& AssetBundle, FName DebugName, TSet<const void*>& AllVisitedStructValues) const
+{
+	static FName AssetBundlesName = TEXT("AssetBundles");
+	static FName IncludeAssetBundlesName = TEXT("IncludeAssetBundles");
+	
+	//根据当前对象的值，搜索拥有AssetBundles的属性的值，最后AddBundleAsset，BundleName就是设置的值，而FoundRef是引用的对象的资产路径
+	else if (const FObjectProperty* ObjectProperty = CastField<FObjectProperty>(Property))
+	{
+		if (ObjectProperty->PropertyFlags & CPF_InstancedReference || ObjectProperty->GetOwnerProperty()->HasMetaData(IncludeAssetBundlesName))
+		{
+			const UObject* Object = ObjectProperty->GetObjectPropertyValue(PropertyValue);
+			if (Object != nullptr)
+			{
+				InitializeAssetBundlesFromMetadata_Recursive(Object->GetClass(), Object, AssetBundle, Object->GetFName(), AllVisitedStructValues);
+			}
+		}
+	}
+}
+```