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

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Numeric/ArrayClamp/ArrayClamp.md

@@ -0,0 +1,60 @@
+# ArrayClamp
+
+- **功能描述：** 限定整数属性的值必须在指定数组的合法下标范围内，[0,ArrayClamp.Size()-1]
+- **使用位置：** UPROPERTY
+- **引擎模块：** Numeric Property
+- **元数据类型：** int32
+- **限制类型：** int32
+- **常用程度：** ★★★
+
+限定整数属性的值必须在指定数组的合法下标范围内，[0,ArrayClamp.Size()-1]
+
+## 测试代码：
+
+```cpp
+public:
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = ArrayClampTest)
+	int32 MyInt_NoArrayClamp = 0;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = ArrayClampTest, meta = (ArrayClamp = "MyIntArray"))
+	int32 MyInt_HasArrayClamp = 0;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = ArrayClampTest)
+	TArray<int32> MyIntArray;
+```
+
+## 测试效果：
+
+可见拥有ArrayClamp的整数值被限制在数组的下标中。
+
+![ArrayClamp](ArrayClamp.gif)
+
+## 原理：
+
+根据指定的数组名称在本类里寻找到Array属性，然后把本整数属性的值Clamp在该数组的下标范围内。
+
+```cpp
+template <typename Type>
+static Type ClampIntegerValueFromMetaData(Type InValue, FPropertyHandleBase& InPropertyHandle, FPropertyNode& InPropertyNode)
+{
+	Type RetVal = ClampValueFromMetaData<Type>(InValue, InPropertyHandle);
+
+	//enforce array bounds
+	const FString& ArrayClampString = InPropertyHandle.GetMetaData(TEXT("ArrayClamp"));
+	if (ArrayClampString.Len())
+	{
+		FObjectPropertyNode* ObjectPropertyNode = InPropertyNode.FindObjectItemParent();
+		if (ObjectPropertyNode && ObjectPropertyNode->GetNumObjects() == 1)
+		{
+			Type LastValidIndex = static_cast<Type>(GetArrayPropertyLastValidIndex(ObjectPropertyNode, ArrayClampString));
+			RetVal = FMath::Clamp<Type>(RetVal, 0, LastValidIndex);
+		}
+		else
+		{
+			UE_LOG(LogPropertyNode, Warning, TEXT("Array Clamping isn't supported in multi-select (Param Name: %s)"), *InPropertyHandle.GetProperty()->GetName());
+		}
+	}
+
+	return RetVal;
+}
+```