Don't reference rows before they're put on the stack

1 files changed, 17 insertions, 13 deletions

diff --git a/project2/variables.cpp b/project2/variables.cpp
index cafb336..9aa1a5b 100644
--- a/project2/variables.cpp
+++ b/project2/variables.cpp
@@ -63,23 +63,25 @@ class VariableUri : public VariableImplDyn {
 
 class VariableParent : public VariableImplDyn, public RowUser {
 	public:
-		VariableParent(const Glib::ustring & src, RowUser * dep) :
-			VariableImplDyn(Glib::ustring(std::find_if(src.begin(), src.end(), isalpha), src.end()))
+		VariableParent(const Glib::ustring & src, const RowUser * d) :
+			VariableImplDyn(Glib::ustring(std::find_if(src.begin(), src.end(), isalpha), src.end())),
+			row(NULL),
+			depth(src.length() - source.length()),
+			dep(d)
 		{
-			PerRowValues::RowValuesStack::const_iterator r = PerRowValues::Stack().end();
-			size_t p = src.length() - source.length();
-			while (--p) {
-				r--;
-			}
-			row = *r;
-			row->use(this);
-			if (dep) {
-				row->use(dep);
-			}
 		}
 		const Glib::ustring & value() const
 		{
 			if (!cacheValid) {
+				if (!row) {
+					PerRowValues::RowValuesStack::const_reverse_iterator r = PerRowValues::Stack().rbegin();
+					for (size_t p = depth; --p; r++) ;
+					row = *r;
+					row->use(this);
+					if (dep) {
+						row->use(dep);
+					}
+				}
 				cache = row->getCurrentValue(source);
 				cacheValid = true;
 			}
@@ -90,7 +92,9 @@ class VariableParent : public VariableImplDyn, public RowUser {
 			cacheValid = false;
 		}
 	protected:
-		const PerRowValues * row;
+		mutable const PerRowValues * row;
+		const size_t depth;
+		const RowUser * dep;
 };
 
 class VariableParse : public VariableImplDyn, public RowUser {