'Re: [Kde-bindings] Qt, Qyoto buttons work intermediately'

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List: kde-bindings
Subject: Re: [Kde-bindings] Qt, Qyoto buttons work intermediately
From: Linuxoid Oz <linuxoidoz () yahoo ! com ! au>
Date: 2010-02-16 21:52:56
Message-ID: 971068.50140.qm () web111015 ! mail ! gq1 ! yahoo ! com
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I've read that thing about the signals/slots and that was exactly what I \
was trying to do (at least I thought that was exactly what they said). \
Here's an example from a Qt Address Book tutorial:

 connect(nextButton, SIGNAL(clicked()), this, SLOT(next()));

As the QMessageBox needs a parent reference, 'this' is fine for the \
MainWindow. This is my slot:

QObject.Connect(btnAbout, Qt.SIGNAL("clicked()"), mainwin, 
Qt.SLOT("ShowAbout(mainwin, page)"));

First, the Qt one doesn't have these " ", so I thought it might be a Qyoto \
thing. 'this' is a reference to MainWindow. In my StartWindow, 'mainwin' is \
a reference to the MainWindow. If I use a slot in MainWindow I pass the \
slot a 'this' reference as in the example. If I use a slot in the \
StartWindow I pass it a reference to MainWindow as 'mainwin'.

Are you saying if I declare the SecondWindow class as inherited from \
:QWidget I should then pass the reference to itself as 'this' rather than a \
reference to the MainWindow?

In the StartWindow the QMessageBox also needs a parent reference, that's \
why I pass 'mainwin'  - reference to parent MainWindow. What do you mean by \
passing a type rather than a variable? How do you pass a type if you need \
to pass a reference to the parent window? If I pass anything else it \
complains that that reference doesn't exist in the current context.

Yes. You didn't understand how signals and slots work. This explains it \
all:  http://doc.trolltech.com/4.6/signalsandslots.html .

Short summery: This line
QObject.Connect(btnAbout, Qt.SIGNAL("clicked()"), mainwin, 
Qt.SLOT("ShowAbout(mainwin, page)"));
connects to a method (slot) ShowAbout() which takes two arguments: one of \
type  mainwin, one of type page. There are two reasons why this won't work:

1. The signal doesn't provide any parameters, but the slot does. How is \
this  supposed to work?
2. You give a method signature to the SLOT method, i.e. mainwin and page \
are  expected to be types, not variables. But there is no type called \
'mainwin' and  there is also no type called 'page'. Both are variables. But \
this is not how  signals and slots work. SIGNAL and SLOT expect \
_signatures_, not method call  expressions.

Furthermore, you can only define slots in QObject subclasses. Otherwise you \
 have to use delegate connections. (QObject.Connect(sender, \
SIGNAL(/*signal*/),  delegate { /* ... */ });)

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<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" \
style="font: inherit;">I've read that thing about the signals/slots and \
that was exactly what I was trying to do (at least I thought that was \
exactly what they said). Here's an example from a Qt Address Book \
tutorial: connect(nextButton, SIGNAL(clicked()), this, \
SLOT(next())); As the QMessageBox needs a parent reference, 'this' \
is fine for the MainWindow. This is my \
slot: QObject.Connect(btnAbout, Qt.SIGNAL("clicked()"), mainwin, \
Qt.SLOT("ShowAbout(mainwin, page)")); First, the Qt one doesn't have \
these " ", so I thought it might be a Qyoto thing. 'this' is a reference to \
MainWindow. In my StartWindow, 'mainwin' is a reference to the MainWindow. \
If I use a slot in MainWindow I pass the slot a 'this' reference as in the \
example. If I use a slot in the StartWindow I pass it a reference to \
MainWindow as 'mainwin'. Are you saying if I declare the \
SecondWindow class as inherited from :QWidget I should then pass the \
reference to itself as 'this' rather than a reference to the \
MainWindow? In the StartWindow the QMessageBox also needs a parent \
reference, that's why I pass 'mainwin'&nbsp; - reference to parent \
MainWindow. What do you mean by passing a type rather than a variable? How \
do you pass a type if you need to pass a reference to the parent window? If \
I pass anything else it complains that that reference doesn't exist in the \
current context. <blockquote style="border-left: 2px solid rgb(16, \
16, 255); margin-left: 5px; padding-left: 5px;"><div class="plainMail">Yes. \
You didn't understand how signals and slots work. This explains it all: \
 <a href="http://doc.trolltech.com/4.6/signalsandslots.html" \
target="_blank">http://doc.trolltech.com/4.6/signalsandslots.html</a> \
. Short summery: This line QObject.Connect(btnAbout, \
Qt.SIGNAL("clicked()"), mainwin, Qt.SLOT("ShowAbout(mainwin, \
page)")); connects to a method (slot) ShowAbout() which takes two \
arguments: one of type mainwin, one of type page. There are two reasons \
why this won't work: 1. The signal doesn't provide any parameters, \
but the slot does. How is this supposed to work? 2. You give a \
method signature to the SLOT method, i.e. mainwin and page are expected \
to be types, not variables. But there is no type called 'mainwin' and \
 there is also no type called 'page'. Both are variables. But this is \
not how signals and slots work. SIGNAL and SLOT expect _signatures_, \
not method call expressions. Furthermore, you can only define \
slots in QObject subclasses. Otherwise you have to use delegate \
connections. (QObject.Connect(sender, SIGNAL(/*signal*/), delegate { /* \
... */ });) </div></blockquote></td></tr></table>

      &nbsp;

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