'QObject& QObject::operator=(const QObject&)' is private——無法將自訂的QObject子類放入Qt容器（container）中

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先貼出問題的代碼：

 1 #include<QCoreApplication> 2 classMyObject:publicQObject 3 { 4 public: 5 MyObject(QObject*parent =0): 6 QObject(parent) 7 { 8 } 9 private:10 int m_id;11 };12 int main(int argc,char*argv[])13 {14 QCoreApplication a(argc, argv);15 QList<MyObject>list;16 list<<MyObject(0);17 return a.exec();18 }

 

 編譯後有以下錯誤，非常多： 總結一下問題：MyObject是繼承於QObject的子類，當將其的執行個體放入Qt的容器中（如QList、QHash等），就會報以上錯誤。關於原因，官方文檔裡有以下說明：

QObject has neither a copy constructor nor an assignment operator. This is by design. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). In fact, all Qt classes derived from QObject (direct or indirect) use this macro to declare their copy constructor and assignment operator to be private. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page.

The main consequence is that you should use pointers to QObject (or to your QObject subclass) where you might otherwise be tempted to use your QObject subclass as a value. For example, without a copy constructor, you can‘t use a subclass of QObject as the value to be stored in one of the container classes. You must store pointers.

 

簡單說就是：

QObject的拷貝建構函式是私人的，當把其子類放入容器時無法完成構造其副本。

解決方案就是，使用指標。將自訂的子類以指標的形式儲存在容器中。

 

QList<MyObject *>list;

 

'QObject& QObject::operator=(const QObject&)' is private——無法將自訂的QObject子類放入Qt容器（container）中