experimental: get_property and create_property

src/OpenVolumeMesh/Core/ResourceManager.hh

@@ -41,12 +41,17 @@
 #include <vector>
 #include <type_traits>
 
+#include "../System/Compiler.hh"
 #include "../Config/Export.hh"
 #include "OpenVolumeMeshProperty.hh"
 #include "PropertyHandles.hh"
 #include "TypeName.hh"
 #include "ForwardDeclarations.hh"
 
+#if OVM_CXX_17
+#include <optional>
+#endif
+
 namespace OpenVolumeMesh {
 
 // Forward declarations
@@ -141,6 +146,18 @@ public:
     template<typename T, typename EntityTag>
     PropertyTT<T, EntityTag> request_property(const std::string& _name = std::string(), const T _def = T());
 
+#if OVM_CXX_17
+    /** Create new property: if the property already exists, return no value.
+     */
+    template<typename T, typename EntityTag>
+    std::optional<PropertyTT<T, EntityTag>> create_property(const std::string& _name = std::string(), const T _def = T());
+
+    /** Get existing property: if the property does not exist, return no value.
+     */
+    template<typename T, typename EntityTag>
+    std::optional<PropertyTT<T, EntityTag>> get_property(const std::string& _name = std::string());
+#endif
+
     template<class T> VertexPropertyT<T> request_vertex_property(const std::string& _name = std::string(), const T _def = T());
 
     template<class T> EdgePropertyT<T> request_edge_property(const std::string& _name = std::string(), const T _def = T());

src/OpenVolumeMesh/Core/ResourceManagerT_impl.hh

@@ -123,6 +123,28 @@ PropertyTT<T, EntityTag> ResourceManager::request_property(const std::string& _n
     return internal_create_property<T, EntityTag>(_name, _def);
 }
 
+#if OVM_CXX_17
+
+template<typename T, typename EntityTag>
+std::optional<PropertyTT<T, EntityTag>>
+ResourceManager::create_property(const std::string& _name, const T _def)
+{
+    auto *prop = internal_find_property<T, EntityTag>(_name);
+    if (prop)
+        return {};
+    return {*internal_create_property<T, EntityTag>(_name, _def)};
+}
+
+template<typename T, typename EntityTag>
+std::optional<PropertyTT<T, EntityTag>>
+ResourceManager::get_property(const std::string& _name)
+{
+    auto *prop = internal_find_property<T, EntityTag>(_name);
+    if (prop)
+        return {*prop};
+    return {};
+}
+#endif
 
 
 template<typename T, class EntityTag>