[Qt-interest] Problem with qSort and QObjects

[Thiago Macieira]

Em Terça-feira 16. Fevereiro 2010, às 07.11.38, Carl Snellman escreveu:
> Now, would it make sense to add a few lines to qSort(..) docs to
> describe the requirement that the objects must implement copy
> constructor also? I spent several hours with this... Or is this common
> knowledge that I have just missed on my exploration journey with Qt?

No, because it's not a qSort requirement. It's a QList requirement, which is 
shared with all the other container classes.

For a container class, its element type must be default-constructible, 
copyable, assignable, destructible and assignable. For QMap, it must also be 
orderable (operator<).

If you look at the error message you posted:

In constructor 'Account::Account(const Account&)':
main.cpp:7: instantiated from 'T QList<T>::value(int) const [with T = 
Account]'
main.cpp:35: instantiated from here
/home/maemo/qtsdk-2010.01/qt/include/QtCore/qobject.h:309: error:
'QObject::QObject(const QObject&)' is private

It's telling you that the copy constructor is private. That means QObject is 
not copyable. So the compiler is telling you everything you need to know.

Maybe this is the first time you ran into that error. Fair enough, the first 
time is always the most difficult one. But now you know.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358
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