new update_value in category

include/cif++/category.hpp

@@ -964,6 +964,32 @@ class category
 
 	// --------------------------------------------------------------------
 
+	using value_provider_type = std::function<std::string_view(std::string_view)>;
+
+	/// \brief Update a single item named @a item_name in the rows that match
+	/// \a cond to values provided by a callback function \a value_provider
+	/// making sure the linked categories are updated according to the link.
+	/// That means, child categories are updated if the links are absolute
+	/// and unique. If they are not, the child category rows are split.
+
+	void update_value(condition &&cond, std::string_view item_name,
+		value_provider_type &&value_provider)
+	{
+		auto rs = find(std::move(cond));
+		std::vector<row_handle> rows;
+		std::copy(rs.begin(), rs.end(), std::back_inserter(rows));
+		update_value(rows, item_name, std::move(value_provider));
+	}
+
+	/// \brief Update a single item named @a item_name in the rows \a rows
+	/// to values provided by a callback function \a value_provider
+	/// making sure the linked categories are updated according to the link.
+	/// That means, child categories are updated if the links are absolute
+	/// and unique. If they are not, the child category rows are split.
+
+	void update_value(const std::vector<row_handle> &rows, std::string_view item_name,
+		value_provider_type &&value_provider);
+
 	/// \brief Update a single item named @a item_name in the rows that match \a cond to value \a value
 	/// making sure the linked categories are updated according to the link.
 	/// That means, child categories are updated if the links are absolute
@@ -982,7 +1008,10 @@ class category
 	/// That means, child categories are updated if the links are absolute
 	/// and unique. If they are not, the child category rows are split.
 
-	void update_value(const std::vector<row_handle> &rows, std::string_view item_name, std::string_view value);
+	void update_value(const std::vector<row_handle> &rows, std::string_view item_name, std::string_view value)
+	{
+		update_value(rows, item_name, [value](std::string_view) { return value; });
+	}
 
 	// --------------------------------------------------------------------
 	// Naming used to be very inconsistent. For backward compatibility,

src/category.cpp

@@ -1339,7 +1339,8 @@ std::string category::get_unique_value(std::string_view item_name)
 	return result;
 }
 
-void category::update_value(const std::vector<row_handle> &rows, std::string_view item_name, std::string_view value)
+void category::update_value(const std::vector<row_handle> &rows, std::string_view item_name,
+	value_provider_type &&value_provider)
 {
 	using namespace std::literals;
 
@@ -1352,40 +1353,29 @@ void category::update_value(const std::vector<row_handle> &rows, std::string_vie
 
 	auto &col = m_items[colIx];
 
+	// this is expensive, but better throw early on
 	// check the value
 	if (col.m_validator)
 	{
-		std::error_code ec;
-		col.m_validator->validate_value(value, ec);
-		if (ec)
-			throw validation_exception(ec, m_name, item_name);
-	}
-
-	// first some sanity checks, what was the old value and is it the same for all rows?
-	std::string oldValue{ rows.front()[item_name].text() };
-	for (auto row : rows)
-	{
-		if (oldValue != row[item_name].text())
+		for (auto row : rows)
 		{
-			std::ostringstream os;
+			std::string value{ value_provider(row[item_name].text()) };
 
-			os << "Inconsistent old values in update_value, trying to set " << std::quoted(value)
-			   << " as value for item " << item_name << " in category " << m_name;
-
-			throw std::runtime_error(os.str());
+			std::error_code ec;
+			col.m_validator->validate_value(value, ec);
+			if (ec)
+				throw validation_exception(ec, m_name, item_name);
 		}
 	}
 
-	if (oldValue == value) // no need to do anything
-		return;
-
-	// update rows, but do not cascade
-	for (auto row : rows)
-		row.assign(colIx, value, false);
-
-	// see if we need to update any child categories that depend on this value
+	// update and see if we need to update any child categories that depend on this value
 	for (auto parent : rows)
 	{
+		std::string oldValue{ parent[item_name].text() };
+		std::string value{ value_provider(oldValue) };
+
+		parent.assign(colIx, value, false);
+
 		for (auto &&[childCat, linked] : m_child_links)
 		{
 			if (std::find(linked->m_parent_keys.begin(), linked->m_parent_keys.end(), item_name) == linked->m_parent_keys.end())