Best way for a parent class to know value chosen on child class

[scarecr0w132]

Hello,

I have a MainWindow class, on an action I create a new project type selector.

MainWindow.cpp

...
void MainWindow::on_actionFileNew_triggered()
{
    NewDocumentSelector newdocumentselector;
    newdocumentselector.exec();
}
...

...
void MainWindow::on_actionFileNew_triggered()
{
    NewDocumentSelector newdocumentselector;
    newdocumentselector.exec();
}
...

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I want MainWindow to know the type selected
Should I
1) Emit a signal in NewDocumentSelector and connect it to MainWindow.
or
2) Pass MainWindow into NewDocumentSelector on initilization,

NewDocumentSelector newdocumentselector(MainWindow);

NewDocumentSelector newdocumentselector(MainWindow);

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which will then be used in NewDocumentSelector as

MainWindow.thisTypeSelected();

MainWindow.thisTypeSelected();

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or
Is there another way? I want to follow Qt's MV pattern.
In other words I want to access parent class instance.
I have attached my project if you require more detail.

Thanks