changed find1 a bit more

reverted to returning empty results in case nothing is found

CMakeLists.txt

@@ -35,7 +35,6 @@ include(CheckIncludeFiles)
 include(CheckLibraryExists)
 include(CMakePackageConfigHelpers)
 include(Dart)
-include(GenerateExportHeader)
 
 set(CXX_EXTENSIONS OFF)
 set(CMAKE_CXX_STANDARD 20)
@@ -275,9 +274,6 @@ if(UNIX)
 	target_compile_definitions(cifpp PUBLIC CACHE_DIR="${CIFPP_CACHE_DIR}")
 endif()
 
-# generate_export_header(cifpp
-# 	EXPORT_FILE_NAME cif++/Cif++Export.hpp)
-
 set(INCLUDE_INSTALL_DIR ${CMAKE_INSTALL_INCLUDEDIR})
 set(LIBRARY_INSTALL_DIR ${CMAKE_INSTALL_LIBDIR})
 set(SHARE_INSTALL_DIR ${CMAKE_INSTALL_DATADIR}/libcifpp)

include/cif++/category.hpp

@@ -262,13 +262,7 @@ class category
 	{
 		auto h = find<T>(pos, std::forward<condition>(cond), column);
 
-		if (h.empty())
-			throw std::runtime_error("No hits found");
-
-		if (h.size() != 1)
-			throw std::runtime_error("Hit not unique");
-
-		return std::get<0>(*h.begin());
+		return h.size() == 1 ? std::get<0>(*h.begin()) : T{};
 	}
 
 	template <typename... Ts, typename... Cs, typename U = std::enable_if_t<sizeof...(Ts) != 1>>
@@ -285,13 +279,7 @@ class category
 		static_assert(sizeof...(Ts) == sizeof...(Cs), "The number of column titles should be equal to the number of types to return");
 		auto h = find<Ts...>(pos, std::forward<condition>(cond), std::forward<Cs>(columns)...);
 
-		if (h.empty())
-			throw std::runtime_error("No hits found");
-
-		if (h.size() != 1)
-			throw std::runtime_error("Hit not unique");
-
-		return *h.begin();
+		return h.size() == 1 ? *h.begin() : std::tuple<Ts...>{};
 	}
 
 	bool exists(condition &&cond) const

include/cif++/item.hpp

@@ -292,7 +292,11 @@ struct item_handle
 	{
 	}
 
+	static const item_handle s_null_item;
+
   private:
+	item_handle();
+
 	uint16_t m_column;
 	row_handle &m_row_handle;
 
@@ -421,6 +425,13 @@ struct item_handle::item_value_as<T, std::enable_if_t<std::is_same_v<T, bool>>>
 template <size_t N>
 struct item_handle::item_value_as<char[N]>
 {
+	static std::string convert(const item_handle &ref)
+	{
+		if (ref.empty())
+			return {};
+		return { ref.text().data(), ref.text().size() };
+	}
+
 	static int compare(const item_handle &ref, const char (&value)[N], bool icase)
 	{
 		return icase ? cif::icompare(ref.text(), value) : ref.text().compare(value);
@@ -430,6 +441,13 @@ struct item_handle::item_value_as<char[N]>
 template <typename T>
 struct item_handle::item_value_as<T, std::enable_if_t<std::is_same_v<T, const char *>>>
 {
+	static std::string convert(const item_handle &ref)
+	{
+		if (ref.empty())
+			return {};
+		return { ref.text().data(), ref.text().size() };
+	}
+
 	static int compare(const item_handle &ref, const char *value, bool icase)
 	{
 		return icase ? cif::icompare(ref.text(), value) : ref.text().compare(value);
@@ -439,6 +457,13 @@ struct item_handle::item_value_as<T, std::enable_if_t<std::is_same_v<T, const ch
 template <typename T>
 struct item_handle::item_value_as<T, std::enable_if_t<std::is_same_v<T, std::string_view>>>
 {
+	static std::string convert(const item_handle &ref)
+	{
+		if (ref.empty())
+			return {};
+		return { ref.text().data(), ref.text().size() };
+	}
+
 	static int compare(const item_handle &ref, const std::string_view &value, bool icase)
 	{
 		return icase ? cif::icompare(ref.text(), value) : ref.text().compare(value);

include/cif++/row.hpp

@@ -172,22 +172,22 @@ class row_handle
 
 	item_handle operator[](uint32_t column_ix)
 	{
-		return item_handle(column_ix, *this);
+		return empty() ? item_handle::s_null_item : item_handle(column_ix, *this);
 	}
 
 	const item_handle operator[](uint32_t column_ix) const
 	{
-		return item_handle(column_ix, const_cast<row_handle &>(*this));
+		return empty() ? item_handle::s_null_item : item_handle(column_ix, const_cast<row_handle &>(*this));
 	}
 
 	item_handle operator[](std::string_view column_name)
 	{
-		return item_handle(add_column(column_name), *this);
+		return empty() ? item_handle::s_null_item : item_handle(add_column(column_name), *this);
 	}
 
 	const item_handle operator[](std::string_view column_name) const
 	{
-		return item_handle(get_column_ix(column_name), const_cast<row_handle &>(*this));
+		return empty() ? item_handle::s_null_item : item_handle(get_column_ix(column_name), const_cast<row_handle &>(*this));
 	}
 
 	template <typename... C>
@@ -202,7 +202,7 @@ class row_handle
 		return detail::get_row_result<Ts...>(*this, { get_column_ix(columns)... });
 	}
 
-	template<typename T>
+	template <typename T>
 	T get(const char *column)
 	{
 		return operator[](get_column_ix(column)).template as<T>();

src/item.cpp

@@ -24,14 +24,25 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <cassert>
+
 #include <cif++/row.hpp>
 
 namespace cif
 {
 
+const item_handle item_handle::s_null_item;
+row_handle s_null_row_handle;
+
+item_handle::item_handle()
+	: m_column(std::numeric_limits<uint16_t>::max())
+	, m_row_handle(s_null_row_handle)
+{
+}
+
 std::string_view item_handle::text() const
 {
-	if (m_row_handle.m_row != nullptr)
+	if (not m_row_handle.empty())
 	{
 		for (auto iv = m_row_handle.m_row->m_head; iv != nullptr; iv = iv->m_next)
 		{
@@ -45,6 +56,7 @@ std::string_view item_handle::text() const
 
 void item_handle::assign_value(const item &v)
 {
+	assert(not m_row_handle.empty());
 	m_row_handle.assign(m_column, v.value(), true);
 }
 

src/row.cpp

@@ -31,21 +31,25 @@ namespace cif
 
 void row_handle::assign(size_t column, std::string_view value, bool updateLinked, bool validate)
 {
+	assert(m_category);
 	m_category->update_value(m_row, column, value, updateLinked, validate);
 }
 
 uint16_t row_handle::get_column_ix(std::string_view name) const
 {
+	assert(m_category);
 	return m_category->get_column_ix(name);
 }
 
 std::string_view row_handle::get_column_name(uint16_t ix) const
 {
+	assert(m_category);
 	return m_category->get_column_name(ix);
 }
 
 uint16_t row_handle::add_column(std::string_view name)
 {
+	assert(m_category);
 	return m_category->add_column(name);
 }
 
@@ -53,6 +57,9 @@ uint16_t row_handle::add_column(std::string_view name)
 
 row_initializer::row_initializer(row_handle rh)
 {
+	assert(rh.m_category);
+	assert(rh.m_row);
+
 	row *r = rh;
 	auto &cat = *rh.m_category;