Can now parse optionals, which do not throw an error, if missing.

Author: 5cript

parse/jsd_optional.h

@@ -0,0 +1,28 @@
+#ifndef JSD_OPTIONAL_H_INCLUDED
+#define JSD_OPTIONAL_H_INCLUDED
+
+#include <boost/optional.hpp>
+
+namespace JSON
+{
+    template <typename T>
+    void parse(boost::optional <T>& value, std::string const& name,
+               PropertyTree const& object, ParsingOptions const& options = DEFAULT_PARSER_OPTIONS)
+    {
+        try
+        {
+            auto opt = object.tree.get_optional <T> (name);
+            if (!opt)
+                return; // its ok, it was optional
+            else
+                value = opt.get();
+        }
+        catch (boost::property_tree::ptree_bad_data& exc)
+        {
+			DEFAULT_PROPERTY_ERROR_HANDLER(T(), T());
+        }
+        // cannot throw ptree_bad_path
+    }
+}
+
+#endif // JSD_OPTIONAL_H_INCLUDED