# 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](../EditConditionHides/EditConditionHides.md), [InlineEditConditionToggle](../InlineEditConditionToggle/InlineEditConditionToggle.md), [HideEditConditionToggle](../HideEditConditionToggle/HideEditConditionToggle.md)
- **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：

```cpp
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。

![EditCondition](EditCondition.gif)

## 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。

```cpp
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));
		}
	}
		
}
```