How to create input/output using wildcard in a BP function C++

[Nathanmiguel]

I’m integrating pybind11 and python 3.9.13 as a game plugin to use tensorflow or something else and I need to use wildcard input and output to create a global variables inside python interpeter.

So what I need is: create a “array(FString) or struct” as wildcard, then I need to get variable name, type(like float, bool, text etc…) and its value.

PythonFunctionLibrary.h

public:
        UFUNCTION(BlueprintCallable, Category = "PythonBridge|Execution", CustomThunk, meta = (	Keywords = "Struct python", CustomStructureParam = "AnyStruct" ))
	static int RunPythonScript( FString Script,  UStruct* AnyStruct, UStruct* &Output);
	DECLARE_FUNCTION(execRunPythonScript);

private:
	/* Example function for parsing a single property
	* @param Property    the property reflection data
	* @param ValuePtr    the pointer to the property value
	*/
	static void ReceiveSomeStruct_impl(FProperty* Property, void* StructPtr);
	
	static void ParseProperty(FProperty* Property, void* ValuePtr);

PythonFunctionLibrary.cpp

int UPythonFunctionLibrary::RunPythonScript(FString Script, UStruct* AnyStruct, UStruct* &Output)
{
	check(0);
	return 0;
}

DEFINE_FUNCTION(UPythonFunctionLibrary::execRunPythonScript)
{
	P_GET_OBJECT(UStruct, AnyStruct);

	// Steps into the stack, walking to the next property in it
	Stack.Step(Stack.Object, NULL);

	// Grab the last property found when we walked the stack
	// This does not contains the property value, only its type information
	FProperty* StructProperty = CastField<FProperty>(Stack.MostRecentProperty);

	// Grab the base address where the struct actually stores its data
	// This is where the property value is truly stored
	void* StructPtr = Stack.MostRecentPropertyAddress;

	P_GET_PROPERTY_REF(FStrProperty, Script);

	// Steps into the stack, walking to the next property in it
	Stack.Step(Stack.Object, NULL);

	// Grab the last property found when we walked the stack
	// This does not contains the property value, only its type information
	FProperty* StrProperty = CastField<FProperty>(Stack.MostRecentProperty);

	// Grab the base address where the struct actually stores its data
	// This is where the property value is truly stored
	void* StrPtr = Stack.MostRecentPropertyAddress;

	P_GET_OBJECT(UStruct, Output);

	// We need this to wrap up the stack
	P_FINISH;

	// Iterate through the struct
	ReceiveSomeStruct_impl(StructProperty, StructPtr);
	Output = AnyStruct;
	*(int*)RESULT_PARAM = 0;
}

/*
* Example function for iterating through all properties of a struct
* @param StructProperty    The struct property reflection data
* @param StructPtr        The pointer to the struct value
*/
void UPythonFunctionLibrary::ReceiveSomeStruct_impl(FProperty* Property, void* StructPtr)
{
	UE_LOG(LogTemp, Warning, TEXT("%s"), *Property->GetAuthoredName());
	FStructProperty* StructProperty = CastField<FStructProperty>(Property);
	//check for null
	if (StructProperty)
	{
		// Walk the structs' properties
		for (TFieldIterator<FProperty> PropertyIt(StructProperty->Struct); PropertyIt; ++PropertyIt)
		{
			// This is the variable name if you need it
			UE_LOG(LogTemp, Warning, TEXT("%s"), *PropertyIt->GetAuthoredName());
			// Never assume ArrayDim is always 1
			for (int32 ArrayIndex = 0; ArrayIndex < PropertyIt->ArrayDim; ArrayIndex++)
			{
				// This grabs the pointer to where the property value is stored
				void* ValuePtr = PropertyIt->ContainerPtrToValuePtr<void>(StructPtr, ArrayIndex);

				// Parse this property
				ParseProperty(*PropertyIt, ValuePtr);
			}
		}
	}
}

void UPythonFunctionLibrary::ParseProperty(FProperty* Property, void* ValuePtr)
{
	float FloatValue;
	int32 IntValue;
	bool BoolValue;
	FString StringValue;
	FName NameValue;
	FText TextValue;
	// Here's how to read integer and float properties
	if (FNumericProperty* NumericProperty = CastField<FNumericProperty>(Property))
	{
		if (NumericProperty->IsFloatingPoint())
		{
			FloatValue = NumericProperty->GetFloatingPointPropertyValue(ValuePtr);
			UE_LOG(LogTemp, Warning, TEXT("float:'%f'"), FloatValue);
		}
		else if (NumericProperty->IsInteger())
		{
			IntValue = NumericProperty->GetSignedIntPropertyValue(ValuePtr);
			UE_LOG(LogTemp, Warning, TEXT("integer:'%i'"), IntValue);
		}
	}
	// How to read booleans
	else if (FBoolProperty* BoolProperty = CastField<FBoolProperty>(Property))
	{
		BoolValue = BoolProperty->GetPropertyValue(ValuePtr);
		if (BoolValue) 
		{
			UE_LOG(LogTemp, Warning, TEXT("Bool: True"));
		}
		else 
		{
			UE_LOG(LogTemp, Warning, TEXT("Bool: False"));
		}
	}
	// Reading names
	else if (FNameProperty* NameProperty = CastField<FNameProperty>(Property))
	{
		NameValue = NameProperty->GetPropertyValue(ValuePtr);
		UE_LOG(LogTemp, Warning, TEXT("Name:'%s'"), *NameValue.ToString());
	}
	// Reading strings
	else if (FStrProperty* StringProperty = CastField<FStrProperty>(Property))
	{
		StringValue = StringProperty->GetPropertyValue(ValuePtr);
		UE_LOG(LogTemp, Warning, TEXT("String:'%s'"), *StringValue);
	}
	// Reading texts
	else if (FTextProperty* TextProperty = CastField<FTextProperty>(Property))
	{
		TextValue = TextProperty->GetPropertyValue(ValuePtr);
		UE_LOG(LogTemp, Warning, TEXT("Text:'%s'"), *TextValue.ToString());
	}
	// Reading an array
	else if (FArrayProperty* ArrayProperty = CastField<FArrayProperty>(Property))
	{
		// We need the helper to get to the items of the array       
		FScriptArrayHelper Helper(ArrayProperty, ValuePtr);
		for (int32 i = 0, n = Helper.Num(); i < n; ++i)
		{
			UE_LOG(LogTemp, Warning, TEXT("Array:%i"), i);
			ParseProperty(ArrayProperty->Inner, Helper.GetRawPtr(i));
		}
	}
	// Reading a nested struct
	else if (Property)
	{
		ReceiveSomeStruct_impl(Property, ValuePtr);
	}
}

I change the code that why the input and output are diferent, but I cant do a return as a wildcard using this method.

I wish to do a function like that.