Add RecordSet RowView

This represents a view into a recordset by row number and provides easy
access to values in a column by index and the ability to create a new
object instance by N columns which are passed to the object's
constructor.

1 files changed, 26 insertions, 0 deletions

diff --git a/lib/dbRecordSet.h b/lib/dbRecordSet.h
index 9bddc01..5bd6967 100644
--- a/lib/dbRecordSet.h
+++ b/lib/dbRecordSet.h
@@ -5,6 +5,31 @@
 #include <memory>
 
 namespace MyGrate {
+	class RecordSet;
+
+	class RowView {
+	public:
+		RowView(const RecordSet * rs, std::size_t rw = 0);
+
+		DbValue operator[](std::size_t col) const;
+
+		template<typename S, std::size_t N, typename Indices = std::make_index_sequence<N>>
+		auto
+		create() const
+		{
+			return create<S>(Indices {});
+		}
+
+		template<typename S, std::size_t... I> auto create(std::index_sequence<I...>) const
+		{
+			return std::make_unique<S>((*this)[I]...);
+		}
+
+	private:
+		const RecordSet * recordSet;
+		std::size_t row;
+	};
+
 	class RecordSet {
 	public:
 		virtual ~RecordSet() = default;
@@ -12,6 +37,7 @@ namespace MyGrate {
 		virtual std::size_t rows() const = 0;
 		virtual std::size_t columns() const = 0;
 		virtual DbValue at(std::size_t, std::size_t) const = 0;
+		RowView operator[](std::size_t row) const;
 	};
 	using RecordSetPtr = std::unique_ptr<RecordSet>;
 }