我想存储从一个类继承的QHash
个元素。所以我得到了:
class ImageInterface
{
public:
ImageInterface();
ImageInterface(const QString& path);
virtual QString getName() const = 0;
};
并实施:
class Image : public ImageInterface
{
public:
Image();
Image(const QString& path);
QString getName() const { return name; }
private:
QString name;
};
然后我想在QHash
中使用它:
QHash<QString, ImageInterface> *imageMap;
imageMap = new QHash<QString, ImageInterface>();
ImageInterface *im = new Image(var);
imageMap->insert(im->getName(), *im);
imageMap->take(name);
有错误。
../EmulatorKamery/mainwindow.cpp:59:28: error: cannot allocate an object of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: because the following virtual functions are pure within ‘ImageInterface’:
../EmulatorKamery/imageinterface.h:13:25: note: virtual QString ImageInterface::getName() const
In file included from /usr/include/qt4/QtCore/qvariant.h:50:0,
from /usr/include/qt4/QtCore/qabstractitemmodel.h:45,
from /usr/include/qt4/QtGui/qabstractitemview.h:46,
from /usr/include/qt4/QtGui/qlistview.h:45,
from /usr/include/qt4/QtGui/qlistwidget.h:45,
from /usr/include/qt4/QtGui/QListWidget:1,
from ../EmulatorKamery/mainwindow.h:5,
from ../EmulatorKamery/mainwindow.cpp:1:
/usr/include/qt4/QtCore/qhash.h: At global scope:
/usr/include/qt4/QtCore/qhash.h: In instantiation of ‘QHashNode<QString, ImageInterface>’:
/usr/include/qt4/QtCore/qhash.h:765:9: instantiated from ‘QHash<K, V>::iterator QHash<K, V>::insert(const Key&, const T&) [with Key = QString, T = ImageInterface]’
../EmulatorKamery/mainwindow.cpp:46:48: instantiated from here
/usr/include/qt4/QtCore/qhash.h:221:7: error: cannot declare field ‘QHashNode<QString, ImageInterface>::value’ to be of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
/usr/include/qt4/QtCore/qhash.h: In member function ‘T QHash<K, V>::take(const Key&) [with Key = QString, T = ImageInterface]’:
../EmulatorKamery/mainwindow.cpp:59:28: instantiated from here
/usr/include/qt4/QtCore/qhash.h:805:24: error: invalid abstract return type for member function ‘T QHash<K, V>::take(const Key&) [with Key = QString, T = ImageInterface]’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
../EmulatorKamery/mainwindow.cpp:59:28: instantiated from here
/usr/include/qt4/QtCore/qhash.h:808:18: error: cannot allocate an object of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
/usr/include/qt4/QtCore/qhash.h:813:24: error: cannot allocate an object of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
/usr/include/qt4/QtCore/qhash.h:813:11: error: cannot declare variable ‘t’ to be of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
../EmulatorKamery/mainwindow.cpp:59:28: instantiated from here
/usr/include/qt4/QtCore/qhash.h:819:16: error: cannot allocate an object of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
/usr/include/qt4/QtCore/qhash.h:821:14: error: cannot allocate an object of abstract type ‘ImageInterface’
../EmulatorKamery/imageinterface.h:8:11: note: since type ‘ImageInterface’ has pure virtual functions
/usr/include/qt4/QtCore/qhash.h:822:1: warning: control reaches end of non-void function [-Wreturn-type]
我应该如何实施这样的东西?
答案 0 :(得分:6)
您必须存储指向抽象类型的指针。否则它会尝试实例化该类的实例,但由于它是抽象的,所以它不能实现。
QHash<QString, ImageInterface*> *imageMap;
答案 1 :(得分:4)
您必须在哈希容器中存储指针(或更好的智能指针,如std :: shared_ptr或QSharedPointer)。