From 1eb9007542b1cbfad3e7089d0273ac32b4756d4e Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 24 Sep 2015 02:22:49 +0100
Subject: Add operator>> support to columns

---
 libdbpp/column.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++++
 libdbpp/column.h   |  7 +++++++
 2 files changed, 51 insertions(+)

diff --git a/libdbpp/column.cpp b/libdbpp/column.cpp
index 91d26f5..81150a5 100644
--- a/libdbpp/column.cpp
+++ b/libdbpp/column.cpp
@@ -1,4 +1,6 @@
 #include "column.h"
+#include <boost/utility/enable_if.hpp>
+#include <exception>
 
 DB::Column::Column(const Glib::ustring & n, unsigned int i) :
 	colNo(i),
@@ -10,4 +12,46 @@ DB::Column::~Column()
 {
 }
 
+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 null() override { }
+
+		template <typename D, typename dummy = int>
+		void operator()(const D &,
+				typename boost::disable_if<std::is_convertible<D, T>, dummy>::type = 0) {
+			throw std::runtime_error("Invalid type conversion");
+		}
+
+		template <typename D, typename dummy = int>
+		void operator()(const D & v,
+				typename boost::enable_if<std::is_convertible<D, T>, dummy>::type = 0) {
+			target = (T)v;
+		}
+
+		T & target;
+};
+
+#define COLUMNINTO(Type) \
+void \
+DB::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);
 
diff --git a/libdbpp/column.h b/libdbpp/column.h
index 47492d1..c94cbe3 100644
--- a/libdbpp/column.h
+++ b/libdbpp/column.h
@@ -27,6 +27,13 @@ namespace DB {
 			virtual void apply(HandleField &) const = 0;
 			virtual void rebind(Command *, unsigned int) const = 0;
 
+			void operator>>(std::string &) const;
+			void operator>>(bool &) const;
+			void operator>>(int64_t &) const;
+			void operator>>(double &) const;
+			void operator>>(boost::posix_time::time_duration &) const;
+			void operator>>(boost::posix_time::ptime &) const;
+
 			const unsigned int		colNo;
 			const Glib::ustring		name;
 	};
-- 
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