ALL copyable classes should implement BOTH copy constructor and assignment operator, or none

[jakepetroules]

Any class that is intended to be copyable should override BOTH the copy constructor and the assignment operator, never only one of them. I have experienced real issues with the MSVC compiler when failing to do so.

MyClass(const MyClass &);
MyClass &operator=(const MyClass &);

If the class is not designed to be copied, it MUST disable the operators like so:

class MyClass
{
    Q_DISABLE_COPY(MyClass)
    ....

TLDR; you override both the copy constructor and assignment operator, or disable both.

Some useful info: https://qt-project.org/doc/qt-4.8/qobject.html#Q_DISABLE_COPY