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我无法理解 Q_OBJECT 子类的 QVariant 的行为（GVPalette* 继承自具有 Q_OBJECT 宏的 BasicItemNode）。编译器错误是 

/qobject.h:471:   instantiated from ‘T qobject_cast(QObject*) [with T = GVPalette*]’
/qvariant.h:584:  instantiated from ‘static T QtPrivate::QVariantValueHelper<T>::object(const QVariant&) [with T = GVPalette*]’
/qvariant.h:100:  instantiated from ‘static ReturnType QtPrivate::ObjectInvoker<Derived, Argument, ReturnType>::invok
                  e(Argument)  [with Derived = QtPrivate::QVariantValueHelper<GVPalette*>, 
                  Argument = const QVariant&, ReturnType = GVPalette*]’
/qvariant.h:593:   instantiated from ‘T qvariant_cast(const QVariant&) [with T = GVPalette*]’
/CLSMetaType.cpp:50:   instantiated from here
/BasicItemNode.h:27: error: void value not ignored as it ought to be

下面代码段中的第 2 行对应于 CLSMetaType.cpp:50 和第 6 行。对应于 BasicItemNode.h:27

CLSMetaType.cpp
if(variant.canConvert<GVPalette*>()) {
  1.//retVal = variant.value<GVPalette*>()->objectName();
  2. GVPalette* gv = variant.value<GVPalette*>();
  3. retVal = gv->objectName();
}

BasicItemNode.h
4. class BasicItemNode : public QObject
5. {
6.   Q_OBJECT

Qt5 - 开源版本 g++ - 4.6.3

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