c++ - QVariant 转换为基本类型

Question

我有这样的类(class):

class QObjectDerived : public QObject
{
    Q_OBJECT
    // ...
};
Q_DECLARE_METATYPE(QObjectDerived*)

当这个类被存储到 QVariant 中时，会发生这种行为

  QObjectDerived *object = new QObjectDerived(this);
  QVariant variant = QVariant::fromValue(object);
  qDebug() << variant;                          // prints QVariant(QObjectDerived*, )
  qDebug() << variant.value<QObject*>();        // prints QObject(0x0)
  qDebug() << variant.value<QObjectDerived*>(); // QObjectDerived(0x8c491c8)

  variant = QVariant::fromValue(static_cast<QObject*>(object));
  qDebug() << variant;                          // prints QVariant(QObject*, QObjectDerived(0x8c491c8) )
  qDebug() << variant.value<QObject*>();        // prints QObjectDerived(0x8c491c8)
  qDebug() << variant.value<QObjectDerived*>(); // QObject(0x0)

有没有办法将它存储在 QVariant 中并能够将其作为 QObject* 和 QObjectDerived* 获取？

Answer 1

只能写

QObject *value = variant.value<QObjectDerived*>();

可能可以为您的类型部分特化qvariant_cast，但这不是一个有文档支持的用例，我不愿意依赖它。