#include "params.h"
 
    Params::instance().name = ui->lineEdit->text ().toStdString();
    Params::instance().setNumber (ui->spinBox->value());
 
    Params & p = Params::instance();
    p.getNumber ();

Soubor params.h

#ifndef PARAMS_H
#define PARAMS_H
 
#include <string>
using namespace std;
 
class Params
{
public:
    string name;
 
private:
    int number;
public:
    int getNumber () { return number; }
    void setNumber (int n) { number = n; }
 
public:
    Params();
 
private:
    static int cnt;
    static Params * obj;
 
public:
    static Params & instance ();
};
 
#endif // PARAMS_H

Soubor params.cpp

#include "params.h"
#include <stdexcept>
 
int Params::cnt = 0;
Params * Params::obj = NULL;
 
Params::Params()
{
    cnt ++;
    if (cnt > 1)
       throw new runtime_error ("Too many instances");
}
 
Params & Params::instance ()
{
    if (obj == NULL)
        obj = new Params ();
    return *obj;
}