QMdiArea problem

[walito]

Hi, people, it's my firt post.
Im newbie, and Im problem with QMdiArea.

MdiChild::MdiChild()
{
    setAttribute(Qt::WA_DeleteOnClose);
    isUntitled = true;
}

MdiChild::MdiChild()
{
    setAttribute(Qt::WA_DeleteOnClose);
    isUntitled = true;
}

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mdiArea = new QMdiArea;
    setCentralWidget(mdiArea);
 
    MdiChild *child = new MdiChild;
    mdiArea.addSubWindow(child);
    //mdiArea->addSubWindow(child);

mdiArea = new QMdiArea;
    setCentralWidget(mdiArea);

    MdiChild *child = new MdiChild;
    mdiArea.addSubWindow(child);
    //mdiArea->addSubWindow(child);

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anyone of the 2 options not found.
The error is: 'addSubWindow' has not been declared.

Im not understand, somebody help me?

Sorry my english.
Thz

Walter