Question

I have a widget (mainWidget) and another widget (childWidget), that’s a child of it.

I want to:

connect(childWidget, SIGNAL(somethingHappened(...)), mainWidget, SLOT(handleIt(...));

My question is: does one place the connect statement in mainWidget or childWidget?

• If I create the childWidget in the mainWidget’s constructor and place
  the connect statement on the next line, it works. But, let’s say the
  childWidget, upon being created, does something and then signals to
  the mainWidget success. You could have a situation where the connect
  statement only comes after a function (of childWidget) that emits the
  signal.

• If I place the connect statements in the childWidget’s constructor,
  the problem is that it doesn’t know anything about the parent’s
  slots. If I make childWidget inherit mainWidget, it does know about
  the slots – but this feels like a bad solution to me. Couldn’t get it
  to work anyway. There is probably a proper way to do this – I’m still
  looking.

I’m quite new to Qt programming.
In advance: thank you for any help.

Answer 1

You should design your code well to avoid creeping of mysterious bugs. It would be a better idea to write the connect in the main widget and ideally there should not be an emit in the constructor of the child widget. Possibly you could move out the emit code to another block and do the call after construction is complete. Sub-classing ‘childwidget’ from ‘mainWidget’ only to get access to its slot looks like an inflexible design. Design should be such that if any class knows the signal your class emits, the other class should be able to flexibly connect to it.