Overriding a protected pure virtual function with a signal
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Multiple inheritance with QObject could be problematic. When combining functionality with QObject classes I usually use composition rather than inheritance. I have run into issues with being able to copy objects based upon QObject. It also eliminates the use of templates for those classes. If I need a signal on an object that is not QObject based, and I can't or don't want to inherit from QObject. I will often create a subclass that gets created in the constructor and have it call methods on the parent object. I call this object a signal mule.
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Multiple inheritance with QObject could be problematic. When combining functionality with QObject classes I usually use composition rather than inheritance. I have run into issues with being able to copy objects based upon QObject. It also eliminates the use of templates for those classes. If I need a signal on an object that is not QObject based, and I can't or don't want to inherit from QObject. I will often create a subclass that gets created in the constructor and have it call methods on the parent object. I call this object a signal mule.
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@mooglus said in Overriding a protected pure virtual function with a signal:
Wouldn't you need to define an interface for your mule?
How would that be bad? If I need functionality I code that functionality.
@fcarney It just seems like more typing to provide functionality that inheritance provides. However, if you're in a situation where inheritance is causing you problems then it makes sense. I've read many times that it's good to favour composition over inheritance, in practice I often find it inconvenient. I would upvote you, but your reputation is 666, I could never ruin that ;)
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@fcarney It just seems like more typing to provide functionality that inheritance provides. However, if you're in a situation where inheritance is causing you problems then it makes sense. I've read many times that it's good to favour composition over inheritance, in practice I often find it inconvenient. I would upvote you, but your reputation is 666, I could never ruin that ;)
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@fcarney Interesting reply. I've not run into trouble (yet) with multiple inheritance and Qt. Wouldn't you need to define an interface for your mule? That sounds like a bit of a hassle.
@mooglus said in Overriding a protected pure virtual function with a signal:
I've not run into trouble (yet) with multiple inheritance and Qt.
If you do mean from
QObject(perhaps you don't) then that is surprising. Inheriting from more than oneQObject-derived class is problematic. There are various versions of Qt here, maybe things have changed over the years.https://stackoverflow.com/questions/8578657/qobject-multiple-inheritance/8578921
https://www.ics.com/blog/multiple-inheritance-qt
https://forum.qt.io/topic/88295/with-qt-5-6-is-it-possible-to-avoid-the-diamond-problem-when-signals-and-slots-are-defined-in-two-brancheshttps://doc.qt.io/qt-5/moc.html#multiple-inheritance-requires-qobject-to-be-first
If you are using multiple inheritance, moc assumes that the first inherited class is a subclass of QObject. Also, be sure that only the first inherited class is a QObject.
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I wanted to inherit a templated class with a QObject. I ran into issues. Also multiple QObject inheritance doesn't work either.
@fcarney said in Overriding a protected pure virtual function with a signal:
I wanted to inherit a templated class with a QObject.
Works fine as long as you don't need moc stuff in the template
I ran into issues. Also multiple QObject inheritance doesn't work either.
Can not work to the parent-child relatonsship
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@fcarney said in Overriding a protected pure virtual function with a signal:
I wanted to inherit a templated class with a QObject.
Works fine as long as you don't need moc stuff in the template
I ran into issues. Also multiple QObject inheritance doesn't work either.
Can not work to the parent-child relatonsship
@Christian-Ehrlicher said in Overriding a protected pure virtual function with a signal:
Can not work to the parent-child relatonsship
Nor
moc, more specifically it confuses the hell out of the meta-object system (e.gQMetaObject). -
@fcarney It just seems like more typing to provide functionality that inheritance provides. However, if you're in a situation where inheritance is causing you problems then it makes sense. I've read many times that it's good to favour composition over inheritance, in practice I often find it inconvenient. I would upvote you, but your reputation is 666, I could never ruin that ;)
