[Dbus-cxx-users] MessageAppendIterator::operator<< begin called instead of overload defined in global namespace

[<emm...@or...>]

Hello,

Lately, I have been playing around with DBus-cxx and user-defiend types.

When working with custom types in DBus-cxx, I found that MethodProxy::operator() will call the template member operator<< in MessageAppendIterator instead of the user-defined overload in the global namespace *starting*with*the*second*method*parameter*.
MessageAppendIterator::operator<< in turn attempts to call the MessageAppendIterator::append overload which does not exist and raises a compiler error. This happens at least with GCC 4.6.3

The bug can be reproduced by slightly modifying the time client/server example in examples/basics/types. Just add *two* dummy parameters of type struct timeval to the now() method to trigger this.

As a fix, I propose that MessageAppendIterator::operator<< be modified to delegate its implementation to a template struct with a static append() method. The user would then have to specialize this struct instead of defining his/her own operator<< for custom types. Lazy instantiation of operator<< would ensure that the appropriate specialization is used.

This would also have the benefit of allowing one partial specialization to be used for a broad range of types. As an example, I'm using this to automatically serialize introspectable types (e.g. through boost::enable_if<is_introspectable<T>>::type).

Please see attached patch for the proposed solution. This is a patch against dbus-cxx 0.8.0.

By the way, it would also be nice if deserialization also worked that way. Maybe serialization, deserialization and signature could all rely on a single traits structure as a default?

Regards,

--
Emmanuel
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