string composing of variant type

alib2str/src/container/string/ObjectsVariant.h

+/*
+ * ObjectsVariant.h
+ *
+ * Created on: Sep 27, 2017
+ * Author: Jan Travnicek
+ */
+
+#ifndef _STRING_OBJECTS_VARIANT_H_
+#define _STRING_OBJECTS_VARIANT_H_
+
+#include <alib/variant>
+#include <core/stringApi.hpp>
+
+#include <container/ContainerFromStringLexer.h>
+
+namespace core {
+
+template < class ... Types >
+struct stringApi < ext::variant < Types ... > > {
+	static ext::variant < Types ... > parse ( std::istream & input );
+	static bool first ( std::istream & input );
+	static void compose ( std::ostream & output, const ext::variant < Types ... > & container );
+
+private:
+	class VariantStringApiCallback {
+		std::ostream & m_out;
+	
+	public:
+		VariantStringApiCallback ( std::ostream & out ) : m_out ( out ) {
+		}
+
+		template < class ValueType >
+		void operator ( ) ( const ValueType & value ) {
+			stringApi < ValueType >::compose ( m_out, value );
+		}
+
+		void operator ( ) ( ) {
+			m_out << "void";
+		}
+	};
+};
+
+template < class ... Types >
+ext::variant < Types ... > stringApi < ext::variant < Types ... > >::parse ( std::istream & /* input */ ) {
+	throw exception::CommonException("parsing BarSymbol from string not implemented");
+}
+
+template < class ... Types >
+bool stringApi < ext::variant < Types ... > >::first ( std::istream & /* input */ ) {
+	return false;
+}
+
+template < class ... Types >
+void stringApi < ext::variant < Types ... > >::compose ( std::ostream & output, const ext::variant < Types ... > & container ) {
+	container.template call < void > ( VariantStringApiCallback ( output ) );
+}
+
+} /* namespace core */
+
+#endif /* _STRING_OBJECTS_VARIANT_H_ */