Question

I have a custom class inheriting from QDialog. I’m creating this dialog with function foo, and foo would like to continue doing its thing only when a certain button in the dialog is pressed. I was thinking of using signals and slots, but then how could I get foo to respond to a signal from another thread?

EDIT: basically I want to know how to reimplement the functionality of QInputDialog::getText() using my own dialog.

Answer 1

Your foo() function could call wait() on a [QWaitCondition][1] object, then your button could call wakeOne() on the same object to cause the wait() to return.

That said, there is really no necessity for using multithreading to reimplement QInputDialog::getText(). You should be able to reimplement that functionality inside a single thread without any problems, and doing it that way will be much simpler and more reliable.

(Note: assuming you want your version of getText() to block and not return until after a button is pressed, you’ll need to call QDialog::exec(). I don’t recommend that style of programming though, as it’s error-prone… for example, what happens if the user closes your QInputDialog’s parent window while the QInputDialog is still open? That deletes the QInputDialog object whose getText() method the program is still blocked inside, likely causing a crash because the QInputDialog’s “this” pointer is now a dangling pointer. It’s much cleaner and safer to make everything event-based instead (i.e. signals and slots only), and not attempt to block or recurse Qt’s event loop in your own code)