PyQt4 signals and slots

Question

I am writing my first Python app with PyQt4. I have a MainWindow and a Dialog class, which is a part of MainWindow class: ``` self.loginDialog = LoginDialog(); ``` I use slots and signals. Here's a connection made in MainWindow: ``` QtCore.QObject.connect(self.loginDialog, QtCore.SIGNAL("aa(str)"), self.login) ``` And I try to emit signal inside the Dialog class (I'm sure it is emitted): ``` self.emit(QtCore.SIGNAL("aa"), "jacek") ``` Unfortunately, slot is not invoked. I tried with no arguments as well, different styles of emitting signal. No errors, no warnings in the code. What might be the problem?

Accepted Answer

You don't use the same signal, when emitting and connecting.

`QtCore.SIGNAL("aa(str)")` is not the same as `QtCore.SIGNAL("aa")`. Signals must have the same signature. By the way, if you are defining your own signals, don't define parametres. Just write SIGNAL('aa'), because defining parametres is a thing from C++ and Python version of Qt doesn't need this.

So it should look like this:

```
QtCore.QObject.connect(self.loginDialog, QtCore.SIGNAL("aa"), self.login)
```

and if you pass any parametres in emit, your login method must accept those parametres. Check, if this helps :-)

PyQt4 signals and slots

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