Fully templated extractor

4 files changed, 79 insertions, 69 deletions

diff --git a/libdbpp/column.cpp b/libdbpp/column.cpp
index b660cd3..2028f03 100644
--- a/libdbpp/column.cpp
+++ b/libdbpp/column.cpp
@@ -22,53 +22,20 @@ InvalidConversion::message() const throw()
 	return InvalidConversionMsg::get(from, to);
 }
 
+UnexpectedNullValue::UnexpectedNullValue(const char * const t) : to(t) { }
+
+AdHocFormatter(UnexpectedNullValueMsg, "Unexpected null value in column expecting type (%?)");
+std::string
+UnexpectedNullValue::message() const throw()
+{
+	return InvalidConversionMsg::get(to, to);
+}
+
 void
 DB::HandleField::blob(const DB::Blob &)
 {
 	throw DB::ColumnTypeNotSupported();
 }
 
-template<typename T>
-class Extract : public DB::HandleField {
-	public:
-		Extract(T & t) : target(t) { }
-
-		void floatingpoint(double v) override { (*this)(v); }
-		void integer(int64_t v) override { (*this)(v); }
-		void boolean(bool v) override { (*this)(v); }
-		void string(const char * v, size_t len) override { (*this)(std::string(v, len)); }
-		void timestamp(const boost::posix_time::ptime & v) override { (*this)(v); }
-		void interval(const boost::posix_time::time_duration & v) override { (*this)(v); }
-		void blob(const Blob & v) override { (*this)(v); }
-		void null() override { }
-
-		template <typename D>
-		void operator()(const D & v) {
-			if constexpr (std::is_convertible<D, T>::value) {
-				target = (T)v;
-			}
-			else {
-				throw InvalidConversion(typeid(D).name(), typeid(T).name());
-			}
-		}
-
-		T & target;
-};
-
-#define COLUMNINTO(Type) \
-void \
-Column::operator>>(Type & v) const \
-{ \
-	Extract<Type> e(v); \
-	apply(e); \
-}
-
-COLUMNINTO(bool);
-COLUMNINTO(int64_t);
-COLUMNINTO(double);
-COLUMNINTO(std::string);
-COLUMNINTO(boost::posix_time::ptime);
-COLUMNINTO(boost::posix_time::time_duration);
-COLUMNINTO(Blob);
 }
 
diff --git a/libdbpp/column.h b/libdbpp/column.h
index 393736a..3cc974e 100644
--- a/libdbpp/column.h
+++ b/libdbpp/column.h
@@ -45,30 +45,59 @@ namespace DB {
 			/// Apply a field handler (any sub-class of HandleField)
 			virtual void apply(HandleField &) const = 0;
 
+			template<typename T>
+			class Extract : public DB::HandleField {
+				public:
+					template <typename> struct is_optional {
+						static constexpr bool value = false;
+					};
+					template <typename X> struct is_optional<std::optional<X>> {
+						static constexpr bool value = true;
+					};
+
+					Extract(T & t) : target(t) { }
+
+					void floatingpoint(double v) override { (*this)(v); }
+					void integer(int64_t v) override { (*this)(v); }
+					void boolean(bool v) override { (*this)(v); }
+					void string(const char * v, size_t len) override { (*this)(std::string_view(v, len)); }
+					void timestamp(const boost::posix_time::ptime & v) override { (*this)(v); }
+					void interval(const boost::posix_time::time_duration & v) override { (*this)(v); }
+					void blob(const Blob & v) override { (*this)(v); }
+					void null() override
+					{
+						if constexpr (is_optional<T>::value) {
+							target.reset();
+						}
+						else {
+							throw UnexpectedNullValue(typeid(T).name());
+						}
+					}
+
+					template <typename D>
+					inline
+					void operator()(const D & v)
+					{
+						if constexpr (std::is_assignable<D, T>::value) {
+							target = v;
+						}
+						else if constexpr (std::is_convertible<D, T>::value) {
+							target = (T)v;
+						}
+						else {
+							throw InvalidConversion(typeid(D).name(), typeid(T).name());
+						}
+					}
+
+					T & target;
+			};
+
 			/// STL like string extractor.
-			void operator>>(std::string &) const;
-			/// STL like boolean extractor.
-			void operator>>(bool &) const;
-			/// STL like integer extractor.
-			void operator>>(int64_t &) const;
-			/// STL like numeric extractor.
-			void operator>>(double &) const;
-			/// STL like duration extractor.
-			void operator>>(boost::posix_time::time_duration &) const;
-			/// STL like date time extractor.
-			void operator>>(boost::posix_time::ptime &) const;
-			/// STL like BLOB extractor.
-			void operator>>(Blob &) const;
-			/// STL like wrapper for optional types.
-			template <typename T>
-			void operator>>(std::optional<T> & v) const {
-				if (!isNull()) {
-					v = T();
-					operator>>(*v);
-				}
-				else {
-					v = {};
-				}
+			template<typename T>
+			void operator>>(T & v) const
+			{
+				Extract<T> e(v);
+				apply(e);
 			}
 
 			/// This column's ordinal.
diff --git a/libdbpp/error.h b/libdbpp/error.h
index 6e8ab18..bcb641d 100644
--- a/libdbpp/error.h
+++ b/libdbpp/error.h
@@ -35,6 +35,15 @@ namespace DB {
 			const char * from;
 			const char * to;
 	};
+
+	class DLL_PUBLIC UnexpectedNullValue : public AdHoc::Exception<Error> {
+		public:	
+			UnexpectedNullValue(const char * const from);
+
+		private:
+			std::string message() const throw() override;
+			const char * to;
+	};
 }
 
 #endif
diff --git a/libdbpp/unittests/testUtils.cpp b/libdbpp/unittests/testUtils.cpp
index 30d5bc4..6ff9edd 100644
--- a/libdbpp/unittests/testUtils.cpp
+++ b/libdbpp/unittests/testUtils.cpp
@@ -82,7 +82,7 @@ BOOST_AUTO_TEST_CASE( stdforOverRowsStructuredBinding )
 	int64_t totalOfa = 0;
 	std::string totalOfc;
 	auto sel = db->select("SELECT a, c FROM forEachRow ORDER BY a DESC");
-	for (const auto [ a, c ] : sel->as<int64_t, std::string>()) {
+	for (const auto [ a, c ] : sel->as<int64_t, std::string_view>()) {
 		count += 1;
 		totalOfa += a;
 		totalOfc += c;
@@ -170,9 +170,11 @@ BOOST_AUTO_TEST_CASE( bulkLoadFile )
 		});
 }
 
-BOOST_AUTO_TEST_CASE( nullBind )
+typedef boost::mpl::list<std::string, std::string_view, Glib::ustring> StringTypes;
+BOOST_AUTO_TEST_CASE_TEMPLATE( nullBind, Str, StringTypes )
 {
 	auto db = DB::MockDatabase::openConnectionTo("pqmock");
+	db->execute("DELETE FROM forEachRow");
 	auto ins = db->modify("INSERT INTO forEachRow VALUES(?, ?, ?, ?, ?, ?)");
 	ins->bindParamI(0, std::optional<int>());
 	ins->bindParamF(1, std::optional<double>());
@@ -183,9 +185,12 @@ BOOST_AUTO_TEST_CASE( nullBind )
 	ins->execute();
 	auto sel = db->select("SELECT a, b, c, d, e, f FROM forEachRow WHERE a IS NULL AND b IS NULL AND c IS NULL AND d IS NULL AND e IS NULL AND f IS NULL");
 	unsigned int count = 0;
-	for (const auto & row : sel->as<>()) {
-		(void)row;
+	for (const auto & row : sel->as<int, std::optional<double>, Str>()) {
 		count += 1;
+		BOOST_CHECK_THROW(row.template get<0>(), DB::UnexpectedNullValue);
+		auto nd = row.template get<1>();
+		BOOST_CHECK(!nd.has_value());
+		BOOST_CHECK_THROW(row.template get<2>(), DB::UnexpectedNullValue);
 	}
 	BOOST_REQUIRE_EQUAL(1, count);
 }