Improvements to Spirit Qi Qt QString custom_string.cpp example

[Mateusz Loskot]

Tim Angus asked me to submit this patch (Boost Trac was complaining for him with "Submission rejected as potential spam").

There is an example of how to use Qi with a custom string (in this case a QString from the Qt framework). This is very helpful but it doesn't work in conjunction with the debug facilities. The following patch fixes this by adding a couple of template specialisations.

Patch:

Index: libs/spirit/example/qi/custom_string.cpp
===================================================================
--- libs/spirit/example/qi/custom_string.cpp	(revision 85071)
+++ libs/spirit/example/qi/custom_string.cpp	(working copy)
@@ -34,6 +34,26 @@
             return true;
         }
     };
+
+    // Test if a QString is empty (required for debug)
+    template <>
+    struct is_empty_container<QString>
+    {
+        static bool call(QString const& c)
+        {
+            return c.isEmpty();
+        }
+    };
+
+    // Define how to stream a QString (required for debug)
+    template <typename Out, typename Enable>
+    struct print_attribute_debug<Out, QString, Enable>
+    {
+        static void call(Out& out, QString const& val)
+        {
+            out << val.toStdString();
+        }
+    };

[anonymous]

This is great ! I has exactly the same problem (debugging QStrings did no longer work after a Qt update) and this solved it. Many thanks !

[Joel de Guzman]

Could you please prepare a pull request instead: ​https://github.com/boostorg/spirit

[Mateusz Loskot]

@djowel Sure, here it is ​https://github.com/boostorg/spirit/pull/73