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List:       pykde
Subject:    [PyQt] QString mutable, unicode string immutable
From:       Wolfgang Rohdewald <wolfgang () rohdewald ! de>
Date:       2009-02-26 21:58:35
Message-ID: 200902262258.36751.wolfgang () rohdewald ! de
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Hi,

I just found out the hard way what the subject says

Now I am curious: The PyQt roadmap says that non-pythonic classes
like QString will be removed. So the result of some Qt/KDE methods
will no longer return a mutable result but an immutable result.
Could this not break code that relies on the result being mutable?

This is the concrete case I had:

In a class derived from kdeui.KConfigSkeleton:
(this code is edited to a minimum, might not run)

self._value = QString()
self.configValue = self.addItemString('value',self._value,QString('default'))

after the config dialog I save the new value elsewhere:

saveValue = config.configValue.value()

now saveValue is a QString

after next config dialog I check if the value changed:

if saveValue != config.configValue.value():
  self.applyChanges()

but since theye are QStrings, they are always identical - 
the config dialog also changes my saveValue.

of course the solution is simple: saveValue = str(config.configValue.value())



-- 
Wolfgang
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