I have a small exercise purely in C++ with a slot this way:

Calculator.h:

Qt Code: 
  1. #ifndef CALCULATOR_H
  2. #define CALCULATOR_H
  3.  
  4. #include <QDialog>
  5.  
  6. class QLineEdit;
  8.  
  9. class Calculator : public QDialog
  10. {
  11.     Q_OBJECT
  12.  
  13. public:
  14.     explicit Calculator(QWidget *parent = 0);
  15. private slots:
  16.     void myslot(QString);
  17. private:
  18.     QLineEdit* lineEdit;
  19.     QPushButton* oneButton;
  20.     QPushButton* twoButton;
  21.     QPushButton* quitButton;
  22. };
  23.  
  24. #endif // CALCULATOR_H
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Calculator.cpp is this:

Qt Code: 
  1. #include "calculator.h"
  2. #include <QPushButton>
  3. #include <QLineEdit>
  4. #include <QVBoxLayout>
  5.  
  6. Calculator::Calculator(QWidget *parent)
  7.     : QDialog(parent)
  8. {
  9.     lineEdit = new QLineEdit;
  10.     oneButton = new QPushButton("1");
  11.     twoButton = new QPushButton("2");
  12.     quitButton = new QPushButton("Quit");
  13.  
  14.     QVBoxLayout* vbox = new QVBoxLayout;
  15.     vbox -> addWidget (lineEdit);
  16.     vbox -> addWidget (oneButton);
  17.     vbox -> addWidget (twoButton);
  18.     vbox -> addWidget (quitButton);
  19.  
  20.     setLayout(vbox);
  21.  
  22.     QString st1 = "1";
  23.     QString st2 = "2";
  24.     connect(oneButton, SIGNAL(clicked()), this, SLOT(myslot(st1)));
  25.     connect(twoButton, SIGNAL(clicked()), this, SLOT(myslot(st2)));
  26.     connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
  27. }
  28.  
  29. void Calculator::myslot(QString str)
  30. {
  31.     lineEdit -> setText(str);
  32. }
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And main.cpp is this way:

Qt Code: 
  1. #include <QApplication>
  2. #include "calculator.h"
  3.  
  4. int main(int argc, char* argv[])
  5. {
  6.     QApplication app(argc, argv);
  7.     Calculator calculator;
  8.     calculator.show();
  9.     return app.exec();
  10. }
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The app runs without errors but nothing will be shown in the lineEdit when clicking oneButton and twoButton! And also there are warning messages in the Application Output saying:


QObject::connect: No such slot Calculator::myslot(st1) in ..\Calculator\calculator.cpp:24
QObject::connect: No such slot Calculator::myslot(st2) in ..\Calculator\calculator.cpp:25

What is the reason and how to use a slot in Qt like a function in C++ please?