I've recently implemented a command design pattern in Java with the use of:
private HashMap<Component, CommandInterface> commands;
Where Component
is any Java Component ( JButton
, JMenuItem
, ...) and CommandInterface
is an interface for my Command-Classes.
So my question is: How can I accomplish this with C++/Qt ?
I've already used QMap
and QHash
, but both of them need an overloaded operator ( operator<
or operator==
) for their Key
-values.
Is the only possible way to derive from QObject
and overload operator<
?
Thanks in advance.
One very important difference between Java and C++ is that C++ makes a distinction between an object pointer (reference in Java) QObject* o;
and an object value QObject o;
That being said, Qt strongly encourages to create the QObject on the heap (using new). So you end up with QObject pointers QObject*
. Then your hashmap will work because comparing the pointers is like comparing integers.
QHash<QObject*, CommandInterface*> commands;
Do not forget to manage the lifetime of your objects though, you do not have a garbage collector like in Java. You can use the Qt tree ownership for convenience, depending on your needs : http://doc.qt.io/qt-5/objecttrees.html
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