New helpers to handle variant data

GeoModelCore/GeoModelHelpers/GeoModelHelpers/variantHelpers.h

+// Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
+
+/*
+ * This header file provides helper C++ functions used in GeoModel IO code. 
+ *
+ *  Author:     Riccardo Maria BIANCHI @ CERN
+ *  Created on: April, 2024
+ *
+ */
+
+
+#ifndef GEOMODELHELPERS_VARIANTHELPERS_H
+#define GEOMODELHELPERS_VARIANTHELPERS_H
+
+#include <iostream> 
+#include <string> 
+#include <vector> 
+#include <variant> 
+#include <type_traits> 
+
+
+namespace GeoModelHelpers {
+
+    class variantHelper
+    {
+    public:
+
+        static void printStdVectorVariants(const std::vector<std::variant<int, long, float, double, std::string>> vec)
+        {
+            for (const auto &item : vec)
+            {
+                if (std::holds_alternative<int>(item))
+                    std::cout << std::get<int>(item);
+                else if (std::holds_alternative<long>(item))
+                    std::cout << std::get<long>(item);
+                else if (std::holds_alternative<float>(item))
+                    std::cout << std::get<float>(item);
+                else if (std::holds_alternative<double>(item))
+                    std::cout << std::get<double>(item);
+                else if (std::holds_alternative<std::string>(item))
+                    std::cout << std::get<std::string>(item);
+
+                std::cout << ", ";
+            }
+                std::cout << std::endl;
+        }
+
+        static std::string getFromVariant_String(const std::variant<int, long, float, double, std::string> &record, std::string_view logMsg = "")
+        {
+            std::string_view type{"string"};
+            std::string ret;
+            try
+            {
+                ret = std::get<std::string>(record);
+            }
+            catch (std::bad_variant_access const &ex)
+            {
+                std::cout << ex.what() << ": '" << logMsg << "'  is not a 'string'!\n";
+            }
+            return ret;
+        }
+        static int getFromVariant_Int(const std::variant<int, long, float, double, std::string> &record, std::string_view logMsg = "")
+        {
+            std::string_view type{"int"};
+            int ret;
+            
+            try
+            {
+                ret = std::get<int>(record);
+            }
+            catch (std::bad_variant_access const &ex)
+            {
+                std::cout << ex.what() << ": '" << logMsg << "'  is not a '" << type << "'!\n";
+            }
+            return ret;
+        }
+        static int getFromVariant_Double(const std::variant<int, long, float, double, std::string> &record, std::string_view logMsg = "")
+        {
+            std::string_view type{"double"};
+            double ret;
+            try
+            {
+                ret = std::get<double>(record);
+            }
+            catch (std::bad_variant_access const &ex)
+            {
+                std::cout << ex.what() << ": '" << logMsg << "'  is not a '" << type << "'!\n";
+            }
+            return ret;
+        }
+        static std::string getFromVariant_Type(const std::variant<int, long, float, double, std::string> &record)
+        {
+            std::string type;
+            if (std::holds_alternative<int>(record))
+            {
+                type = "int";
+            }
+            else if (std::holds_alternative<long>(record))
+            {
+                type = "long";
+            }
+            else if (std::holds_alternative<float>(record))
+            {
+                type = "float";
+            }
+            else if (std::holds_alternative<double>(record))
+            {
+                type = "double";
+            }
+            else if (std::holds_alternative<std::string>(record))
+            {
+                type = "string";
+            } else {
+                type = "UNKOWN";
+            }
+            std::cout << "Variant is of type '" << type << "'" << std::endl;
+            return type;
+        }
+    };
+} // end of namespace
+
+
+#endif
+