Qt4: How to change the default values (range, value, single step size) for QSpinBox for new instances?

Question

I'm using lot of QDoubleSpinBoxes in my project (with Qt 4.8.0), and for all of them, I want the same range, single step size, value etc., which are different from the default values though.

I wanted to ask: Is there a way to change these default values so that new instances of the QSpinBoxes will be created with the new default values so that I don't to have change in every time?

Simply said, instead of this:

QDoubleSpinBox *spin1 = new QDoubleSpinBox(this);
spin1->setSingleStep(0.03);
spin1->setDecimals(4);
spin1->setRange(2.0, 35.0);

QDoubleSpinBox *spin2 = new QDoubleSpinBox(this);
spin2->setSingleStep(0.03);
spin2->setDecimals(4);
spin2->setRange(2.0, 35.0);

...

I want something like this:

QDoubleSpinBox::setDefaultSingleStep(0.03);
QDoubleSpinBox::setDefaultDecimals(4);
QDoubleSpinBox::setDefaultRange(2.0, 35.0);

QDoubleSpinBox *spin1 = new QDoubleSpinBox(this);
QDoubleSpinBox *spin2 = new QDoubleSpinBox(this);

Does anyone know if this is possible and if yes, how?

Answer 1

You can make a factory, that creates the spin boxes with the desired values.

e.g.

class MySpinBoxFactory {
public:
   MySpinboxFactory(double singleStep, int decimals, double rangeMin, double rangeMax)
   : m_singleStep(singleStep), m_decimals(decimals), m_rangeMin(rangeMin), m_rangeMax(rangeMax) {}

   QDoubleSpinBox *createSpinBox(QWidget *parent = NULL) {
      QDoubleSpinBox *ret = new QDoubleSpinBox(parent);
      ret->setSingleStep(m_singleStep);
      ret->setDecimals(m_decimals);
      ret->setRange(m_rangeMin, m_rangeMax);
      return ret;
   }
private:
   double m_singleStep;
   int m_decimals;
   double m_rangeMin;
   double m_rangeMax;
}

// ...
MySpinboxFactory fac(0.03, 4, 2.0, 35.0);
QDoubleSpinBox *spin1 = fac.createSpinBox(this);
QDoubleSpinBox *spin2 = fac.createSpinBox(this);

You can also add setters to change the values. With this, you can create spinboxes with different default values using a single factory instance.

MySpinboxFactory fac(0.03, 4, 2.0, 35.0);
QDoubleSpinBox *spin1 = fac.createSpinBox(this);
QDoubleSpinBox *spin2 = fac.createSpinBox(this);

fac.setSingleStep(0.1);
QDoubleSpinBox *spin3 = fac.createSpinBox(this);