[Qt-interest] QList and QUrl problem

[ice stone]

Thank you for the detailed explanation. I see that setUrl is the culprit. So for now I will just create a new QUrl object for appending each time.
 
Yan

--- On Fri, 3/26/10, Denis Akhmetzyanov <dakhmetzyanov at smartlabs.tv> wrote:


From: Denis Akhmetzyanov <dakhmetzyanov at smartlabs.tv>
Subject: Re: [Qt-interest] QList and QUrl problem
To: "ice stone" <icestone6124 at yahoo.com>
Cc: qt-interest at trolltech.com
Date: Friday, March 26, 2010, 8:18 AM


Hi,
QUrl class is implicit sharing and QUrl::setUrl() method internally doesn't call to detach() (review src of Qt 4.6.2). Some methods do that, for example:
setScheme(), setAuthority(), setUserInfo(), setUserName(), setPassword(), setHost(), setPort(), setPath(), setEncodedQuery(). I.e. this code works fine:
    QList<QUrl> test;
    QUrl url;
    url.setPath("1");
    test.append(url);
    qDebug()<<test[0];
    url.setPath("2");
    test.append(url);
    qDebug()<<test[0];
    url.setPath("3");
    test.append(url);
    qDebug()<<test[0] << test[1] << test[2];

Output:


#yiv1579852865 p, #yiv1579852865 li {white-space:pre-wrap;}







 QUrl( "1" )  
 QUrl( "1" )  
 QUrl( "1" )   QUrl( "2" )   QUrl( "3" )  
Causes of this behaviour of the QUrl::setUrl() are unknown for me (may be "value object" pattern). So for add different urls you could use:
    QList<QUrl> test;
    test.append(QUrl("1"));
    test.append(QUrl("2"));
    test.append(QUrl("3"));
    qDebug()<<test[0] << test[1] << test[2];

Output is:


#yiv1579852865 p, #yiv1579852865 li {white-space:pre-wrap;}






 QUrl( "1" )   QUrl( "2" )   QUrl( "3" )  



2010/3/26 ice stone <icestone6124 at yahoo.com>






I am trying to figure out a problem involving QList<QUrl>. Here is my code:
 
 QList<QUrl> test;
 QUrl url;
 url.setUrl("1");
 test.append(url);
 qDebug()<<test[0];
 url.setUrl("2");
 test.append(url);
 qDebug()<<test[0];
 url.setUrl("3");
 test.append(url);
 qDebug()<<test[0] << test[1] << test[2];

 
And the output is:
 QUrl( "1" )  
 QUrl( "2" )  
 QUrl( "3" )   QUrl( "3" )   QUrl( "3" )
 
My understanding of QList is that it allocates a memory in heap for every inserted item and delete them when they are removed from the list. But the output here seems to point to a single QUrl object for all three items. Anyone can help me to solve this puzzle? Thanks a lot.
 
Yan

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