connect()中slot定义的变迁

随着C++的演进, 代码的写作方式也会发生变化.

这是Qt5之前的时代的Demo里面的写法, 当需要将slot函数作为参数传递的时候, 使用的是SLOT()宏. 

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fontColorToolButton->setMenu(createColorMenu(SLOT(textColorChanged()), Qt::black));
...
fillColorToolButton->setMenu(createColorMenu(SLOT(itemColorChanged()), Qt::white));
...


QMenu *MainWindow::createColorMenu(const char *slot, QColor defaultColor)
{
    ...
    QMenu *colorMenu = new QMenu(this);
    for (int i = 0; i < colors.count(); ++i) {
        QAction *action = new QAction(names.at(i), this);
        action->setData(colors.at(i));
        action->setIcon(createColorIcon(colors.at(i)));
        connect(action, SIGNAL(triggered()), this, slot);
        ...
        colorMenu->addAction(action);
    }
    return colorMenu;
}

而在进入Qt6时代后, 基于C++17, 官方Demo也悄然发生了改变:

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fillColorToolButton = new QToolButton;
fillColorToolButton->setPopupMode(QToolButton::MenuButtonPopup);
fillColorToolButton->setMenu(createColorMenu(&MainWindow::itemColorChanged, Qt::white));
...
lineColorToolButton->setMenu(createColorMenu(&MainWindow::lineColorChanged, Qt::black));


template<typename PointerToMemberFunction>
QMenu *MainWindow::createColorMenu(const PointerToMemberFunction &slot, QColor defaultColor)
{
    colors << Qt::black << Qt::white << Qt::red << Qt::blue << Qt::yellow;
    QStringList names;
    names << tr("black") << tr("white") << tr("red") << tr("blue") << tr("yellow");

    QMenu *colorMenu = new QMenu(this);
    for (int i = 0; i < colors.count(); ++i) {
        QAction *action = new QAction(names.at(i), this);
        action->setData(colors.at(i));
        action->setIcon(createColorIcon(colors.at(i)));
        connect(action, &QAction::triggered, this, slot);
        colorMenu->addAction(action);
        if (colors.at(i) == defaultColor)
            colorMenu->setDefaultAction(action);
    }
    return colorMenu;
}