全选，取消全选

要实现全选和取消全选，可以在该类中添加两个槽函数，分别实现全选和取消全选的功能。例如：

void RSCheckComboBox::selectAll()
{
    QStandardItemModel *model = qobject_cast<QStandardItemModel*>(view()->model());
    if (model) {
        for (int i = 0; i < model->rowCount(); ++i) {
            QModelIndex index = model->index(i, 0);
            model->setData(index, Qt::Checked, Qt::CheckStateRole);
        }
    }
}

void RSCheckComboBox::deselectAll()
{
    QStandardItemModel *model = qobject_cast<QStandardItemModel*>(view()->model());
    if (model) {
        for (int i = 0; i < model->rowCount(); ++i) {
            QModelIndex index = model->index(i, 0);
            model->setData(index, Qt::Unchecked, Qt::CheckStateRole);
        }
    }
}

然后在全选和取消全选的按钮的槽函数中分别调用这两个函数即可。