[Interest] Best way to invoke a slot after some time with QObject::sender

Preet prismatic.project at gmail.com
Tue Aug 28 10:22:51 CEST 2012

>> I have a project where I'm trying to asynchronously reply to a signal.
>> So if ObjectA sends ObjectB a signal, ObjectB will send ObjectA a
>> reply signal at some later point in time.
> That sounds like "broken by design" to me: you'd have a dependency circle here! In order to *connect* to a signal you have to *know* the signal emiter's class. So signals should only go one way: bottom up.

Yeah, it's a little broken :)  All the objects that are talking to
each other in my scenario are actually plugins. I couldn't come up
with a way to tell a potential plugin dev how to 'talk' to my ObjectB
plugin without directly saying "give your plugin a slot called
"onSomeSignal()" if you want me to talk to you!"

> That said, your problem sounds a little bit what QNetworkAccessManager is solving: you have multiple clients that request (by method call!) something from the network, they get a handle (object) for the time being (with which they can also e.g. abort the current operation), the QNAM does its work asynchronously and finally emits a signal (actually several ones in each state transition) once it's done (it doesn't know its clients though!).
> Why wouldn't that approach work in your case?

I like this idea a lot... its a bit more work, but at least it'd let
me adhere to the observer pattern. I'm gonna try and implement it,
thanks for the idea!

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