API中没有重载函数，但实际用时有重载函数

QSpinBox *spin = new QSpinBox(this);

QSlider *slider = new QSlider(Qt::Horizontal, this); 

 QHBoxLayout *hlayout = new QHBoxLayout(this);

hlayout->addWidget(spin); hlayout->addWidget(slider); 

connect(spin, &QSpinBox::valueChanged, slider, &QSlider::setValue);