BlueRoseNote/03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/DetailsPanel/EditCondition/EditCondition.md

EditCondition

• 功能描述： 给一个属性指定另外一个属性或者表达式来作为是否可编辑的条件。
• 使用位置： UPROPERTY
• 引擎模块： DetailsPanel
• 元数据类型： string="abc"
• 关联项： EditConditionHides, InlineEditConditionToggle, HideEditConditionToggle
• 常用程度： ★★★★★

给一个属性指定另外一个属性或者表达式来作为是否可编辑的条件。

• 表达式里引用的属性必须得是同一个类或结构范围内的。

测试代码：

UCLASS(BlueprintType)
class INSIDER_API UMyProperty_EditCondition_Test :public UObject
{
	GENERATED_BODY()
public:
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = Property)
	bool MyBool;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = Property)
	int32 MyInt = 123;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = Property, meta = (EditCondition = "MyBool"))
	int32 MyInt_EditCondition = 123;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = Property, meta = (EditCondition = "!MyBool"))
	int32 MyInt_EditCondition_Not = 123;

public:
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PropertyExpression)
	int32 MyFirstInt = 123;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PropertyExpression)
	int32 MySecondInt = 123;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PropertyExpression, meta = (EditCondition = "(MyFirstInt+MySecondInt)==500"))
	int32 MyInt_EditConditionExpression = 123;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PropertyExpression, meta = (EditCondition = "!((MyFirstInt+MySecondInt)==500)"))
	int32 MyInt_EditConditionExpression_Not = 123;
};

测试结果：

• 可以通过bool单个属性来控制其他属性是否可以编辑
• 也可以通过一个表达式引入更复杂的计算机制来决定是否来编辑。

原理：

在细节面板的属性初始化的时候，会判断该属性EditCondition设置，如果有值，会创建FEditConditionParser来解析表达式然后求值。

void FPropertyNode::InitNode(const FPropertyNodeInitParams& InitParams)
{
	const FString& EditConditionString = MyProperty->GetMetaData(TEXT("EditCondition"));

	// see if the property supports some kind of edit condition and this isn't the "parent" property of a static array
	const bool bIsStaticArrayParent = MyProperty->ArrayDim > 1 && GetArrayIndex() != -1;
	if (!EditConditionString.IsEmpty() && !bIsStaticArrayParent)
	{
		EditConditionExpression = EditConditionParser.Parse(EditConditionString);
		if (EditConditionExpression.IsValid())
		{
			EditConditionContext = MakeShareable(new FEditConditionContext(*this));
		}
	}
		
}