Key press event in a templated class

reactive

I just discovered that Q_OBJECTs and templates don't mix. I have a small templated
class that needs to listen for a QLineEdit's returnPressed signal. What is the best way
to do this? With installEventFilter? What is the event code? Thanks!

goetz

You can create a private helper class which inherits QObject, instantiate one object in your template class and use this as the receiver for the signal (connect is a static method - your template class can just call QObject::connect(...))

reactive

The difficulty for me is, this helper class would need a reference to an instance of a template class. Can I do that without the helper class being templated? The only kludgey way I can
see to do this is to use a helper class and an interface. I'm new at C++ templates so
maybe I'm missing something.

Here's some pseudo-code.

This is what I wish I could do, but can't because of the q_object/template thing:

@
template <class T>
class Foo {

constructor {
QTableView table...
connect(table, doubleClicked, doubleClicked)
}

slot doubleClicked {
T t = ... calculated from QModelIndex
handler.handle(t)
}

Handler<T> handler; // member

}
@

This is my hack. How can I do this better?

@
class Interface { public: callBackIndex(QModelIndex) }

class Helper {

Q_OBJECT

slot doubleClicked { callback.callbackIndex(QModelIndex); }

Interface callback; // member

}

template <class T>
class Foo : public Interface {

constructor {
QTableView table...
connect(table, doubleClicked, helper.doubleClicked)
}

callbackIndex {
T t = ... calculated from QModelIndex
handler.handle(t)
}

Helper helper (this); // member
Handler<T> handler; // member

}

@

The handler is being passed into Foo and Foo has a couple other templated members as well.
I just don't know how to pass in a reference to Foo in Helper without Helper being templated as well.
If I try to pass it in as a pointer with no template parameter it is an error: Helper::Helper(Foo* foo)

reactive

Bump.

Franzk

Depending on what T you intend your template for, you can consider using QVariant instead.