Reading examples and documentation I start to believe that making a custom SIGNAL is not a difficult task. Trying to do it though I realize that I cannot do it!!

Here's a simple example, that if I understand it I will be able to make more custom signals.

  1. a line edit for number A
  2. a line edit for number B
  3. a line edit to present the result of the Multiplication


Here is the corresponding code:


Qt Code: 
  1. MyDialog::MyDialog(QWidget *parent)
  2.     : QWidget(parent)
  3. {
  4.  
  5.     QLineEdit *numberA = new QLineEdit;
  6.     QLineEdit *numberB  = new QLineEdit;
  7.  
  8.     result  = new QLineEdit;
  9.  
  10.     numberA->setText("1.0");
  11.     numberB->setText("1.0");
  12.     result->setText("1.0");
  13.  
  14.  
  15.  
  16.     vboxlayout = new QVBoxLayout(this);
  17.     vboxlayout->addWidget(numberA);
  18.     vboxlayout->addWidget(new QLabel("x"));
  19.     vboxlayout->addWidget(numberB);
  20.     vboxlayout->addWidget(new QLabel("="));
  21.     vboxlayout->addWidget(result);
  22.  
  23.     setLayout(vboxlayout);
  24. }
  25.  
  26.  
  27. void MyDialog::showMultiplication(QString Astring,QString Bstring)
  28. {
  29.     double A,B,Res;
  30.     QString ResString;
  31.  
  32.  
  33.     A= Astring.toDouble();
  34.     B= Bstring.toDouble();
  35.  
  36.  
  37.     Res = A*B;
  38.  
  39.     ResString.setNum(Res);
  40.  
  41.     result->setText(ResString);
  42. }
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QUESTION:
When the user inserts a new number (anywhere A or B) the multiplication result should be shown directly in the result line edit. The SLOT is obliously the showMultiplication(QString Astring,QString Bstring).

The SIGNAL should be something like
sendNewNumbersForMultiplication(QString ,QString )

BUT, I really cannot understand how to implement it!!
Any help?