How to broadcast a signal in Qt4

I'm wanting a paradigm in a Qt4 (PyQt4) program where a component is able to respond to a signal without knowing anything about where it is coming from.

My intial rea开发者_JAVA技巧ding suggests that I have to explicitly connect signals to slots. But what I want is for any of a number of components to be able to send a signal, and for it to be processed by another component.

Comparing with another toolkits, for example, in wxWidgets I would use events. These automatically propogate up from child windows/objects to parents. At each level they can be handled. This means if I have a lot of children which may emit the same event, I don't have to explicitly connect all of them to the handler. I can just put the handler in the parent, or some higher level in the window hierarchy. This means that only the event generator and consumer need to know about the event at all. The consumer doesn't need to know where the source of the event is, how many such sources there are, or anything else about it.

Is this possible in Qt - is there another approach? Maybe there is an alternative event mechanism to signals and slots?

This isn't easily possible - you have to have something that knows about the signaling object and the receiving object to connect the two. Depending on what you need, however, you might be able to set up a class that mediates between the two (so objects with signals tell the class they exist, and have such-and-such a signal, while objects with slots tell the class they exist and have such-and-such a slot to connect to a given signal, and the mediator class tracks both of those, making connections when necessary).

Don't you just want a good old fashioned method invocation? The response is just the return value of the method.

Signal handlers do NOT know the emitter (only the signal type) and emitters do NOT know what handlers are connected. Many handlers can connect to the same signal and they are executed in the order of connection. A signal can be emitted from many places.