I think the multiple inheritance route is just fine, to consider your abstract
class as a mixin. The signal support is not a problem, since it will be
processed as part of the QObject's metaclass.
It's not legal to inherit from multiple QObjects, and you would see this when
you try and call the constructor on both, which means it doesn't even really
make sense to use a QObject as the base type of your mixin.
class Abstract(QtGui.QWidget):
pass
class Imp(QtGui.QLineEdit, Abstract):
def __init__(self):
QtGui.QLineEdit.__init__(self)
# Abstract.__init__(self) # <-- not legal
# RuntimeError: You can't initialize an object twice!
Just use object or some other non-qt type. And the naming scheme of
AbstractMixin, to me, indicates that it is to be used as a mixin and doesn't
have a custom constructor.
But, the addition of your own metaclass to the mixin will result in a conflict
like this:
TypeError: Error when calling the metaclass bases
metaclass conflict: the metaclass of a derived class must be a (non-strict)
subclass of the metaclasses of all its bases
I've actually used this python recipe to support Qt mixins that have a
metaclass and it worked great:
http://code.activestate.com/recipes/204197-solving-the-metaclass-conflict/
On Oct 27, 2013, at 2:25 AM, Marcus Ottosson wrote:
> This is more of a general programming question, but I figured it applies to
> Qt programming in particular and I keep encountering it without finding any
> nice enough solution.
>
> I usually write an abstract interface for a set of classes and put
> dependencies on the interface rather than their implementations.
>
> When subclassing QWidget however, how can you make an interface for
> subclasses of an already implemented class? Is multiple inheritance a good
> idea in this scenario?
>
> Currently, I'm writing the interface as a subclass of QWidget, is this a good
> way?
>
> Thanks,
> Marcus
>
>
> --
> Marcus Ottosson
> [email protected]
>
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