[PyKDE] qt.qApp, subclassing QApplication
dan at tombstonezero.net
dan at tombstonezero.net
Sat Jan 17 17:45:00 GMT 2004
On Thu, 15 Jan 2004 19:15:06 +0000,
Phil Thompson <phil at riverbankcomputing.co.uk> wrote:
> On Thursday 15 January 2004 10:58 am, axel.mittendorf at transfertech.de wrote:
> > in my application I want to subclass qt.QApplication and use
> > this subclass instead of QApplication. Some of my modules are
> > automatically generated by pyuic and I am not allowed to
> > change their source code. The problem is these modules do
> > "from qt import *" and use an object called "qApp" which seems
> > to be an instance of qt.Application and I want them to use my
> > subclass (exactly its instance) instead of "qApp". How can I
> > solve this?
> What makes you think that qApp doesn't refer to the instance of
> your QApplication sub-class?
I have this same issue. In specific answer to your question,
here's an excerpt from my program:
class MyApp( QApplication ):
def __init__( self, argv ):
QApplication.__init__( self, argv )
if __name__ == "__main__":
app = MyApp( sys.argv )
w = MyWidget( )
app.setMainWidget( w )
print 'main:', app
print 'main:', qApp
and its output:
main: <__main__.MyApp object at 0xf2690>
main: <__main__.qt.QApplication object at 0xf2330>
qApp does *not* refer to the instance of my subclass.
> > I wondered to overwrite qApp with my instance, does this
> > work? Or will "qApp" be overwritten when a module does
> > "from qt import *"?
> You can overwrite it, but you have to make sure you do it in the
> right place. Something like...
> import sys
> import qt
> sys.modules['qt'].__dict__['qApp'] = your_instance
Where is the right place to do this? Inside MyApp.__init__?
Inside main, after I create app?
Is this still valid/safe in light of my example above?
> However, qApp should already refer to the same C++ instance that
> was created when your sub-class instance was created. The only
> issue you might have is if you need the Python type of qApp to
> be the that of your sub-class instead of QApplication - in which
> case you will have to overwrite it.
That is exactly the case: that IWBNI the type of qApp were my
subclass rather than qApplication. Perhaps this is a design flaw,
but I decided to add some application-wide utility functions to my
application subclass, mostly thin wrappers around "emit( PYSIGNAL(
'somesignal' ), *args )" sorts of utility functions. That way, I
can reference them from anywhere as qApp.utilityfunction.
I hear, and I forget. Dan Sommers
I see, and I remember. [insert your own joke here]
I do, and I understand. <mailto:dan at tombstonezero.net>
-- Confucius <http://www.tombstonezero.net/dan/>
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