WriteJsonUE.cpp

// Create a root JSon object that'll hold all the sub sections
TSharedRef<FJsonObject> RootJson = MakeShareable(new FJsonObject);

// Output the contents of the DevNotes arrays
{
	for (int i = 0; i < m_aNoteContents.Num(); ++i)
	{
		TSharedRef<FJsonObject> SubJson = MakeShareable(new FJsonObject);
		SubJson->SetNumberField(TEXT("X"), m_aNotePositions[i].X);
		SubJson->SetNumberField(TEXT("Y"), m_aNotePositions[i].Y);
		SubJson->SetNumberField(TEXT("Z"), m_aNotePositions[i].Z);
		SubJson->SetStringField(TEXT("Note"), *m_aNoteContents[i]);
		RootJson->SetObjectField(FString::Printf(TEXT("Note_%d"), i), SubJson);
	}
}

// Output the built string to file
{
	FString OutputStr;
	TSharedRef<TJsonWriter<>> Writer = TJsonWriterFactory<>::Create(&OutputStr);
	FJsonSerializer::Serialize(RootJson, Writer);
	FString sFullPath = FPaths::ProjectSavedDir() + _sDevNotesFilename;
	FFileHelper::SaveStringToFile(OutputStr, *sFullPath);
}