[qofinstance.cpp] add overloaded qof_instance_set|get_path_kvp

these overloaded functions to kvp slots do not require GValue

Author: christopherlam

libgnucash/engine/qofinstance-p.h

@@ -36,6 +36,7 @@
 #ifdef __cplusplus
 #include "kvp-frame.hpp"
 #include <string>
+#include <optional>
 extern "C"
 {
 #endif
@@ -165,6 +166,12 @@ void qof_instance_get_path_kvp (QofInstance *, GValue *, std::vector<std::string
 
 void qof_instance_set_path_kvp (QofInstance *, GValue const *, std::vector<std::string> const &);
 
+template <typename T> std::optional<T>
+qof_instance_get_path_kvp (QofInstance*, const Path&);
+
+template <typename T> void
+qof_instance_set_path_kvp (QofInstance*, std::optional<T>, const Path&);
+
 bool qof_instance_has_path_slot (QofInstance const *, std::vector<std::string> const &);
 
 void qof_instance_slot_path_delete (QofInstance const *, std::vector<std::string> const &);

libgnucash/engine/qofinstance.cpp

@@ -1063,6 +1063,32 @@ qof_instance_set_kvp (QofInstance * inst, GValue const * value, unsigned count,
     delete inst->kvp_data->set_path (path, kvp_value_from_gvalue (value));
 }
 
+template <typename T> std::optional<T>
+qof_instance_get_path_kvp (QofInstance* inst, const Path& path)
+{
+    g_return_val_if_fail (QOF_IS_INSTANCE(inst), std::nullopt);
+    auto kvp_value{inst->kvp_data->get_slot(path)};
+    return kvp_value ? std::make_optional<T>(kvp_value->get<T>()) : std::nullopt;
+}
+
+template <typename T> void
+qof_instance_set_path_kvp (QofInstance* inst, std::optional<T> value, const Path& path)
+{
+    g_return_if_fail (QOF_IS_INSTANCE(inst));
+    delete inst->kvp_data->set_path(path, value ? new KvpValue(*value) : nullptr);
+    qof_instance_set_dirty (inst);
+}
+
+template std::optional<const char*> qof_instance_get_path_kvp <const char*> (QofInstance*, const Path&);
+template std::optional<gnc_numeric> qof_instance_get_path_kvp <gnc_numeric> (QofInstance*, const Path&);
+template std::optional<GncGUID*> qof_instance_get_path_kvp <GncGUID*> (QofInstance*, const Path&);
+template std::optional<int64_t> qof_instance_get_path_kvp <int64_t> (QofInstance*, const Path&);
+
+template void qof_instance_set_path_kvp <const char*> (QofInstance*, std::optional<const char*>, const Path& path);
+template void qof_instance_set_path_kvp <gnc_numeric> (QofInstance*, std::optional<gnc_numeric>, const Path& path);
+template void qof_instance_set_path_kvp <GncGUID*> (QofInstance*, std::optional<GncGUID*>, const Path& path);
+template void qof_instance_set_path_kvp <int64_t> (QofInstance*, std::optional<int64_t>, const Path& path);
+
 void qof_instance_get_path_kvp (QofInstance * inst, GValue * value, std::vector<std::string> const & path)
 {
     gvalue_from_kvp_value (inst->kvp_data->get_slot (path), value);