QVariant::toString and custom data types

[camel]

Something like toString but which can handle user-defined types ?

Not very nice, but you could do something like this:
(insert Pseudo-code/compile on own risk disclaimer here ;-)

Header:

namespace VariantConversion {
   QString (*VariantToStringFunction)(const QVariant &);
 
   void registerVariantToStringFunction(int usertype,
                         VariantToStringFunction function);
 
   QString variantToString(const QVariant &variant);
}

namespace VariantConversion {
   QString (*VariantToStringFunction)(const QVariant &);

   void registerVariantToStringFunction(int usertype,
                         VariantToStringFunction function);

   QString variantToString(const QVariant &variant);
}

To copy to clipboard, switch view to plain text mode 

Implementation

Q_GLOBAL_STATIC(QReadWriteLock, getLock)
typedef QMap<int,  VariantConversion::VariantToStringFunction> FunctionMap;
Q_GLOBAL_STATIC(FunctionMap, getFunctionMap)
 
void VariantConversion::registerVariantToStringFunction(int usertype,
                         VariantToStringFunction function)
{
   QWriteLocker writeLock(&getLock());
   functionMap[usertype] = function;
}
 
QString VariantConversion::variantToString(const QVariant &variant)
{
   int type = variant.userType();
   if (type < QVariant::UserType) {
      return variant.toString();
   }
   QReadLocker readLock(&getLock());
   if (getFunctionMap().contains(type)) {
      return (getFunctionMap()[type])(variant);
   }
   qDebug("No registered function to convert Variant of type "
              "\"%s\" to QString", QMetaType::typeName(type));
   return QString();
}

Q_GLOBAL_STATIC(QReadWriteLock, getLock)
typedef QMap<int,  VariantConversion::VariantToStringFunction> FunctionMap;
Q_GLOBAL_STATIC(FunctionMap, getFunctionMap)

void VariantConversion::registerVariantToStringFunction(int usertype,
                         VariantToStringFunction function)
{
   QWriteLocker writeLock(&getLock());
   functionMap[usertype] = function;
}

QString VariantConversion::variantToString(const QVariant &variant)
{
   int type = variant.userType();
   if (type < QVariant::UserType) {
      return variant.toString();
   }
   QReadLocker readLock(&getLock());
   if (getFunctionMap().contains(type)) {
      return (getFunctionMap()[type])(variant);
   }
   qDebug("No registered function to convert Variant of type "
              "\"%s\" to QString", QMetaType::typeName(type));
   return QString();
}

To copy to clipboard, switch view to plain text mode 

EDIT: I thought about it more, and having a lock in a static variable inside of a function is not the greatest idea, and kind of braindead, at least in older compilers.... (Look up thread safety of static variables)

I do not think Q_GLOBAL_STATIC is public API at this point, but you can find information about it on the web:
http://delta.affinix.com/2006/01/31/q_global_static/
http://article.gmane.org/gmane.comp....vel.core/39118