+ // wrapper object manages optional properties
+ template <class PropertyType>
+ class optional_property
+ {
+ PropertyType m_property;
+ bool m_has_value;
+
+ public:
+ optional_property() : m_has_value(false) {}
+ optional_property(const PropertyType& value) : m_property(value), m_has_value(true) {}
+ const optional_property<PropertyType>& operator=(const PropertyType& rhs) {
+ this->m_property = rhs;
+ this->m_has_value = true;
+ return *this;
+ }
+ bool operator==(const PropertyType& rhs) const { return this->m_property == rhs; }
+ bool operator==(const optional_property<PropertyType>& rhs) const { return this->m_property == rhs.m_property; }
+ operator PropertyType&() { return this->m_property; }
+ void set(const PropertyType& rhs) { this->m_property = rhs; this->m_has_value = true; }
+ void set_has_value(bool has_value = true) { this->m_has_value = has_value; }
+ void reset(const PropertyType& rhs) { this->m_has_value = false; }
+ bool empty() const { return ! m_has_value; }
+ PropertyType& get() { return m_property; }
+ const PropertyType& const_get() const { return m_property; }
+ };
+
+ // wrapper object manages optional properties
+ template <class PropertyType>
+ class optional_container_property
+ {
+ PropertyType m_property;
+
+ public:
+ optional_container_property() {}
+ optional_container_property(const PropertyType& value) : m_property(value) {}
+ const optional_container_property<PropertyType>& operator=(const PropertyType& rhs) {
+ this->Copy(rhs.m_property);
+ return *this;
+ }
+
+ bool operator==(const PropertyType& rhs) const { return this->m_property == rhs; }
+ bool operator==(const optional_property<PropertyType>& rhs) const { return this->m_property == rhs.m_property; }
+ operator PropertyType&() { return this->m_property; }
+ void set(const PropertyType& rhs) { this->m_property = rhs; }
+ void reset(const PropertyType& rhs) { this->clear(); }
+ bool empty() const { return ! this->m_property.HasValue(); }
+ PropertyType& get() { return m_property; }
+ const PropertyType& const_get() const { return m_property; }
+ };