Implement tuple extraction via operator>>

Author: zauguin

hdr/sqlite_modern_cpp.h

@@ -51,17 +51,6 @@ namespace sqlite {
 
 	typedef std::shared_ptr<sqlite3> connection_type;
 
-	template<typename Tuple, int Element = 0, bool Last = (std::tuple_size<Tuple>::value == Element)> struct tuple_iterate {
-		static void iterate(Tuple& t, database_binder& db) {
-			get_col_from_db(db, Element, std::get<Element>(t));
-			tuple_iterate<Tuple, Element + 1>::iterate(t, db);
-		}
-	};
-
-	template<typename Tuple, int Element> struct tuple_iterate<Tuple, Element, true> {
-		static void iterate(Tuple&, database_binder&) {}
-	};
-
 	class row_iterator;
 	class database_binder {
 
@@ -251,12 +240,7 @@ namespace sqlite {
 				return *this;
 			}
 			template<class ...Types>
-			value_type &operator >>(std::tuple<Types...>& values) {
-				assert(!next_index);
-				tuple_iterate<std::tuple<Types...>>::iterate(values, *_binder);
-				next_index = sizeof...(Types) + 1;
-				return *this;
-			}
+			value_type &operator >>(std::tuple<Types...>& values);
 			template<class ...Types>
 			value_type &operator >>(std::tuple<Types...>&& values) {
 				return *this >> values;
@@ -317,6 +301,27 @@ namespace sqlite {
 		mutable value_type value{_binder}; // mutable, because `changing` the value is just reading it
 	};
 
+	namespace detail {
+		template<typename Tuple, int Element = 0, bool Last = (std::tuple_size<Tuple>::value == Element)> struct tuple_iterate {
+			static void iterate(Tuple& t, row_iterator::value_type& row) {
+				row >> std::get<Element>(t);
+				tuple_iterate<Tuple, Element + 1>::iterate(t, row);
+			}
+		};
+
+		template<typename Tuple, int Element> struct tuple_iterate<Tuple, Element, true> {
+			static void iterate(Tuple&, row_iterator::value_type&) {}
+		};
+	}
+
+	template<class ...Types>
+	row_iterator::value_type &row_iterator::value_type::operator >>(std::tuple<Types...>& values) {
+		assert(!next_index);
+		detail::tuple_iterate<std::tuple<Types...>>::iterate(values, *this);
+		next_index = sizeof...(Types) + 1;
+		return *this;
+	}
+
 	inline row_iterator database_binder::begin() {
 		return row_iterator(*this);
 	}