I want to write a code that increases the value in the line edit when the checkbox is clicked.

[wtimm]

void Widget::on_mt_IncreaseValueButton_clicked()
{
auto originalLength = ui->mt_SerialNumberLineEdit->text().length();
auto val = ui->mt_SerialNumberLineEdit->text().toInt();
val += ui->mt_SpinBox->value();
ui->mt_SerialNumberLineEdit->setText(QString::number(val));
ui->mt_SerialNumberLineEdit->setText(QString::number(val).rightJustified(originalLength , '0'));
}

How can I print and read the val variable here in the file ? I also want it to overwrite the value continuously.

[wtimm]

bool WriteFile(){

QFile file("mt_SerialNumber.txt");

QTextStream stream(&file);
while(val != NULL)
{
    stream << QString::number(val);
}

return true;

}

I defined something like this to main.cpp, but it says undeclared identifier because I can't pull val

[Pl45m4]

@wtimm

Do you even read what we write?

I defined something like this to main.cpp, but it says undeclared identifier because I can't pull val

Because you probably dont have val in your main.cpp. Return it there from your object instance of your widget.

[wtimm]

i tried to return but i got a error message like void function should not return a value

[mrjj]

@wtimm
that means you have something like

void func() {
return 20;
}

so you need to change the return type unless its a slot as then it wont work as you think.

[JonB]

@wtimm
I do not mean to be unkind, but do you not think you should read some books or tutorials about C++ programming? From your problems you need to understand some of the basics, your questions are not really about Qt.

[wtimm]

@Pl45m4 yes val in widget.cpp

[wtimm]

By pressing the grab data button, the value in the serial number
I am printing to text file

when i reopen the project or widget again how can I extract the value from the file and show it in the serial number line edit every time?

[Christian Ehrlicher]

@wtimm said in I want to write a code that increases the value in the line edit when the checkbox is clicked.:

how can I extract the value from the file

open the file and read the content maybe?

[JonB]

@wtimm
It's just the same as where we advised you to use QSettings for this from the start. It is simply (a bit) more complicated with saving to a file yourself. You will still have to write just the same type of code to read the saved value and set into your line edit.

[wtimm]

        QFile inputFile(QString("C:/Users/Hakan/Desktop/Qt Businees/da/mt_SerialNumber.txt"));
        inputFile.open(QIODevice::ReadOnly);
        if (!inputFile.isOpen())
            return;

        QTextStream stream(&inputFile);
        for (QString line = stream.readLine();
             
             !line.isNull();
             line = stream.readLine()) {
            /* process information */
        };

I wrote a code like this but i couldn't get it to print serial number automatically(when i reopen the widget or project)