'QObject& QObject::operator=(const QObject&)' is private——无法将自定义的QObject子类放入Qt容器（con

Posted 2020-08-17 foundkey

先贴出问题的代码：

 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 }

 

 

编译后有以下错误，非常多：

 

总结一下问题：

MyObject是继承于QObject的子类，当将其的实例放入Qt的容器中（如QList、QHash等），就会报以上错误。

关于原因，官方文档里有以下说明：

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.

 

简单说就是：

QObject的拷贝构造函数是私有的，当把其子类放入容器时无法完成构造其副本。

解决方法就是，使用指针。将自定义的子类以指针的形式保存在容器中。

 

QList<MyObject *>list;