Problems with extern int

ConnorFord

I started in python and have migrated to C++ in Qt. I am having problems with variables inside and outside of classes. I've researched everywhere and implemented everything I've found but no progress.

I slashed out the sections of code that shouldn't have any bearing on the code that is related to my problem.

in game.ccp

game::game(QWidget *parent) :
QDialog(parent),
ui(new Ui::game)
{
ui->setupUi(this);
int status = 0;
//int salary = 200;
//QString tot_tokens = QString::number(salary);
//ui->tot_tkn2->setText(tot_tokens);
}
game::~game()
{
delete ui;
}
void game::on_wagerSet_clicked()
{
//QString bet_amount = ui->wagerAmt->text();
//ui->tot_tkn->setText(bet_amount);
extern int status;
if( status==0){
    ui->tot_tkn2->setText("10");
}
}

I am wanting to track and execute certain actions that are dependent on the status of the poker simulator and changes every time the player presses the submit wager button (excess information). I believe my problem has something to do with the extern phrase used but I am unsure

Christian Ehrlicher

'extern int' only tells the compiler that there is a variable somewhere else in your code but nothing more. So you need to define it somewhere otherwise you will get a linker error (when this is the problem you have - you did not tell us) - Basic C problem.

JKSH

@ConnorFord said in Problems with extern int:

game::game(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::game)
{
    ui->setupUi(this);
    int status = 0;
}

Above, status is a local variable which only exists inside your constructor function, game::game(). As soon as a function returns, all of its local variables are destroyed.

From your code snippet, it looks like you want status to be a variable that is linked to your game object and be accessible by other class methods like game::on_wagerSet_clicked() (like creating a Python property called "status"), is that right? If so, you should declare status as a member variable of your game class.

Note: It is not appropriate to use extern here.

class game : public QWidget {

    Q_OBJECT

public:
    game(QWidget *parent = nullptr);
    on_wagerSet_clicked();

    int status() const { return m_status; } // This is a public getter for m_status

private:
    int m_status; // This is a declaration of a private member variable
}