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

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/String/GetOptions/GetOptions.md

@@ -0,0 +1,194 @@
+# GetOptions
+
+- **功能描述：** 指定一个外部类的函数提供选项给FName或FString属性在细节面板中下拉选项框提供值列表。
+- **使用位置：** UPARAM, UPROPERTY
+- **引擎模块：** String/Text Property
+- **元数据类型：** string="abc"
+- **限制类型：** FString,FName
+- **关联项：** [GetKeyOptions](../GetKeyOptions.md), [GetValueOptions](../GetValueOptions.md)
+- **常用程度：** ★★★★★
+
+指定一个外部类的函数提供选项给FName或FString属性在细节面板中下拉选项框提供值列表。
+
+- 只作用于FName或FString属性，FText不支持。
+- 也可以用在容器上，比如TArray，TMap，TSet。
+- 也可用在内部结构的变量上。这里的关键点是在寻找函数的时候，是通过找到OuterObject::Function来的，因此即使是内部结构的变量，也可以找到外部class里的函数。但如果是另外一个不相关的类，就必须用“Module.Class.Function”这种方式才能找到，否则只能返回空。
+- 函数的原型是TArray<FString> FuncName() ，返回一个字符串类型，即使类型是FName，因为引擎内部会自己做转换。
+- 函数可以是成员函数，有可以是静态函数。
+
+## 测试代码：
+
+```cpp
+USTRUCT(BlueprintType)
+struct INSIDER_API FMyOptionsTest
+{
+	GENERATED_BODY()
+public:
+	UPROPERTY(EditAnywhere, meta = (GetOptions = "MyGetOptions_Static"))
+	FString MyString_GetOptions;
+
+	UPROPERTY(EditAnywhere, meta = (GetOptions = "MyGetOptions_Static"))
+	TArray<FString> MyArray_GetOptions;
+
+	UPROPERTY(EditAnywhere, meta = (GetOptions = "MyGetOptions_Static"))
+	TSet<FString> MySet_GetOptions;
+
+	UPROPERTY(EditAnywhere, meta = (GetOptions = "MyGetOptions_Static"))
+	TMap<FString, int32> MyMap_GetOptions;
+};
+
+UCLASS(BlueprintType)
+class INSIDER_API UMyProperty_Text :public UObject
+{
+public:
+	UPROPERTY(EditAnywhere, Category = GetOptions)
+	FString MyString_NoOptions;
+
+	UPROPERTY(EditAnywhere, Category = GetOptions, meta = (GetOptions = "MyGetOptions"))
+	FString MyString_GetOptions;
+
+	UPROPERTY(EditAnywhere, Category = GetOptions, meta = (GetOptions = "MyGetOptions"))
+	FName MyName_GetOptions;
+
+	UPROPERTY(EditAnywhere, Category = GetOptions, meta = (GetOptions = "MyGetOptions"))
+	FText MyText_GetOptions;
+
+	UPROPERTY(EditAnywhere, Category = GetOptions, meta = (GetOptions = "MyGetOptions"))
+	TArray<FString> MyArray_GetOptions;
+
+	UPROPERTY(EditAnywhere, Category = GetOptions, meta = (GetOptions = "MyGetOptions"))
+	TSet<FString> MySet_GetOptions;
+
+	UPROPERTY(EditAnywhere, Category = GetOptions, meta = (GetOptions = "MyGetOptions"))
+	TMap<FString, int32> MyMap_GetOptions;
+
+	UFUNCTION()
+	static TArray<FString> MyGetOptions_Static() { return TArray<FString>{"Cat", "Dog"}; }
+
+	UFUNCTION()
+	TArray<FString> MyGetOptions() { return TArray<FString>{"First", "Second", "Third"}; }
+public:
+	UPROPERTY(EditAnywhere, Category = GetOptionsStruct)
+	FMyOptionsTest MyStruct_GetOptions;
+public:
+	UPROPERTY(EditAnywhere, Category = GetKeyValueOptions, meta = (GetKeyOptions = "MyGetOptions",GetValueOptions="MyGetOptions_Static"))
+	TMap<FString, FName> MyMap_GetKeyValueOptions;
+}
+```
+
+## 测试效果：
+
+根据下图，可见FText并没有起作用。其他带有GetOptions标记的在细节面板上都有一个下拉选项框。
+
+而另外当使用TMap的时候，还可以用GetKeyOptions 和GetValueOptions来分别单独为Key和Value提供不一样的选项列表，见MyMap_GetKeyValueOptions。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+大致流程是用GetPropertyOptionsMetaDataKey来判断一个属性是否支持选项框编辑，然后通过
+
+GetPropertyOptions调用指定的函数来获得选项列表，最后根据这个列表的值BuildComboBoxWidget。
+
+```cpp
+	void PropertyEditorUtils::GetPropertyOptions(TArray<UObject*>& InOutContainers, FString& InOutPropertyPath,
+		TArray<TSharedPtr<FString>>& InOutOptions)
+	{
+		// Check for external function references
+		if (InOutPropertyPath.Contains(TEXT(".")))
+		{
+			InOutContainers.Empty();
+			UFunction* GetOptionsFunction = FindObject<UFunction>(nullptr, *InOutPropertyPath, true);
+
+			if (ensureMsgf(GetOptionsFunction && GetOptionsFunction->HasAnyFunctionFlags(EFunctionFlags::FUNC_Static), TEXT("Invalid GetOptions: %s"), *InOutPropertyPath))
+			{
+				UObject* GetOptionsCDO = GetOptionsFunction->GetOuterUClass()->GetDefaultObject();
+				GetOptionsFunction->GetName(InOutPropertyPath);
+				InOutContainers.Add(GetOptionsCDO);
+			}
+		}
+
+		if (InOutContainers.Num() > 0)
+		{
+			TArray<FString> OptionIntersection;
+			TSet<FString> OptionIntersectionSet;
+
+			for (UObject* Target : InOutContainers)
+			{
+				TArray<FString> StringOptions;
+				{
+					FEditorScriptExecutionGuard ScriptExecutionGuard;
+
+					FCachedPropertyPath Path(InOutPropertyPath);
+					if (!PropertyPathHelpers::GetPropertyValue(Target, Path, StringOptions))
+					{
+						TArray<FName> NameOptions;
+						if (PropertyPathHelpers::GetPropertyValue(Target, Path, NameOptions))
+						{
+							Algo::Transform(NameOptions, StringOptions, [](const FName& InName) { return InName.ToString(); });
+						}
+					}
+				}
+
+				// If this is the first time there won't be any options.
+				if (OptionIntersection.Num() == 0)
+				{
+					OptionIntersection = StringOptions;
+					OptionIntersectionSet = TSet<FString>(StringOptions);
+				}
+				else
+				{
+					TSet<FString> StringOptionsSet(StringOptions);
+					OptionIntersectionSet = StringOptionsSet.Intersect(OptionIntersectionSet);
+					OptionIntersection.RemoveAll([&OptionIntersectionSet](const FString& Option){ return !OptionIntersectionSet.Contains(Option); });
+				}
+
+				// If we're out of possible intersected options, we can stop.
+				if (OptionIntersection.Num() == 0)
+				{
+					break;
+				}
+			}
+
+			Algo::Transform(OptionIntersection, InOutOptions, [](const FString& InString) { return MakeShared<FString>(InString); });
+		}
+	}
+	
+FName GetPropertyOptionsMetaDataKey(const FProperty* Property)
+{
+	// Only string and name properties can have options
+	if (Property->IsA(FStrProperty::StaticClass()) || Property->IsA(FNameProperty::StaticClass()))
+	{
+		const FProperty* OwnerProperty = Property->GetOwnerProperty();
+		static const FName GetOptionsName("GetOptions");
+		if (OwnerProperty->HasMetaData(GetOptionsName))
+		{
+			return GetOptionsName;
+		}
+
+		// Map properties can have separate options for keys and values
+		const FMapProperty* MapProperty = CastField<FMapProperty>(OwnerProperty);
+		if (MapProperty)
+		{
+			static const FName GetKeyOptionsName("GetKeyOptions");
+			if (MapProperty->HasMetaData(GetKeyOptionsName) && MapProperty->GetKeyProperty() == Property)
+			{
+				return GetKeyOptionsName;
+			}
+
+			static const FName GetValueOptionsName("GetValueOptions");
+			if (MapProperty->HasMetaData(GetValueOptionsName) && MapProperty->GetValueProperty() == Property)
+			{
+				return GetValueOptionsName;
+			}
+		}
+	}
+
+	return NAME_None;
+}
+
+TSharedPtr<SWidget> SGraphPinString::TryBuildComboBoxWidget()
+{
+		PropertyEditorUtils::GetPropertyOptions(PropertyContainers, GetOptionsFunctionName, ComboBoxOptions);
+}
+```