TicTacToe, Qt Desktop, Connecting radio buttons

[high_flyer]

I'v tried to use if(rado2->isChecked()) but programm crashes.

Where did you try to use it?
Your code is legal, but very cumbersome, and would not be applicable for any real world application.
Make your self familiar with loops, array/containers.
For example, instead of:

btn1= new QPushButton;
    btn2= new QPushButton;
    btn3= new QPushButton;
    btn4= new QPushButton;
    btn5= new QPushButton;
    btn6= new QPushButton;
    btn7= new QPushButton;
    btn8= new QPushButton;
    btn9= new QPushButton;

btn1= new QPushButton;
    btn2= new QPushButton;
    btn3= new QPushButton;
    btn4= new QPushButton;
    btn5= new QPushButton;
    btn6= new QPushButton;
    btn7= new QPushButton;
    btn8= new QPushButton;
    btn9= new QPushButton;

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You can do:

//Where m_vecButtons is declare in the header as: QVector<QPushButton*> m_vecButtons;
  for(int iBtn = 0; iBtn<9; ++i){
    m_vecButtons.push_back(new QPushButton());
  }

//Where m_vecButtons is declare in the header as: QVector<QPushButton*> m_vecButtons;
  for(int iBtn = 0; iBtn<9; ++i){
    m_vecButtons.push_back(new QPushButton());
  }

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You might also want to have a look at QSignalMapper .