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

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Specifier/UCLASS/UHT/CustomFieldNotify.md

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+# CustomFieldNotify
+
+- **功能描述：** 阻止UHT为该类生成FieldNotify的相关代码。
+
+- **引擎模块：** UHT
+- **元数据类型：** bool
+- **作用机制：** 在ClassFlags中增加[HasCustomFieldNotify](../../../Flags/EClassFlags/HasCustomFieldNotify.md)
+- **常用程度：** 0
+
+阻止UHT为该类生成FieldNotify的相关代码。
+
+在源码里只在UWidget上使用，例如该类里面的bIsEnabled是FieldNotify，正常来说UHT要为其生成代码。但如果该类想自己手动书写这些UHT代码，则可以加上CustomFieldNotify来阻止UHT生成。UWidget的cpp里因为要用别的方式UE_FIELD_NOTIFICATION_IMPLEMENT_CLASS_DESCRIPTOR，因此要拒绝UHT生成。
+
+如果自己的类也要自己UE_FIELD_NOTIFICATION_IMPLEMENT_CLASS_DESCRIPTOR，则可以用上CustomFieldNotify。
+
+## 源码例子：
+
+```cpp
+//E:\P4V\Engine\Source\Runtime\UMG\Public\FieldNotification\FieldNotificationDeclaration.h
+UCLASS(Abstract, BlueprintType, Blueprintable, CustomFieldNotify)
+class UMG_API UWidget : public UVisual, public INotifyFieldValueChanged
+{
+	GENERATED_UCLASS_BODY()
+public:
+	UE_FIELD_NOTIFICATION_DECLARE_CLASS_DESCRIPTOR_BASE_BEGIN(UMG_API)
+		UE_FIELD_NOTIFICATION_DECLARE_FIELD(ToolTipText)
+		UE_FIELD_NOTIFICATION_DECLARE_FIELD(Visibility)
+		UE_FIELD_NOTIFICATION_DECLARE_FIELD(bIsEnabled)
+		UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD_BEGIN(ToolTipText)
+		UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD(Visibility)
+		UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD(bIsEnabled)
+		UE_FIELD_NOTIFICATION_DECLARE_ENUM_FIELD_END()
+	UE_FIELD_NOTIFICATION_DECLARE_CLASS_DESCRIPTOR_BASE_END();
+	
+	
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, FieldNotify, Getter="GetIsEnabled", Setter="SetIsEnabled", BlueprintGetter="GetIsEnabled", BlueprintSetter="SetIsEnabled", Category="Behavior")
+	uint8 bIsEnabled:1;
+	
+	//cpp
+UE_FIELD_NOTIFICATION_IMPLEMENT_CLASS_DESCRIPTOR_ThreeFields(UWidget, ToolTipText, Visibility, bIsEnabled);
+
+```
+
+## 原理：
+
+在判断条件上可见HasCustomFieldNotify的判断。
+
+```cpp
+		protected static bool NeedFieldNotifyCodeGen(UhtClass classObj)
+		{
+			return
+				!classObj.ClassExportFlags.HasAnyFlags(UhtClassExportFlags.HasCustomFieldNotify) &&
+				classObj.ClassExportFlags.HasAnyFlags(UhtClassExportFlags.HasFieldNotify);
+		}
+
+```