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

[JonB]

@wtimm
Please paste code text not screenshots, so others can copy/paste etc.

QString::number(+1) does not add one to anything. And you cannot directly add 1 to U12C5 anyway, since it is not a number. Either convert to a number, add to it, and convert it back to whatever your string represents, or write some code to add to U12C5 in whatever way your addition is supposed to work.

[wtimm]

what should i do to increase the value in such expression?

[JonB]

@wtimm
For that 1111, which is now a number, you could use something like:

auto val = ui->lineEdit->text().toInt();
val += ui->spinBox->value();
ui->lineEdit->setText(QString::number(val));

However, there is something hokey about trying to use a QSpinBox, with its own value and a button, to increase a number in a QLineEdit. In the example you now show, why not make Serial Number a QSpinBox itself and dispense with the separate incrementer and pushbutton?

[wtimm]

ui->spinBox->setValue(08246);

The code throws an error when I enter such a value, so I thought it would be better to use QLineEdit.

[wtimm]

what can i do so that the leading zero doesn't go away

[J.Hilk]

@wtimm

auto val = ui->lineEdit->text().toInt();
auto originalLength = ui->lineEdit->text().length();
val += ui->spinBox->value();
ui->lineEdit->setText(QString::number(val).rightJustified(originalLength, '0'));

[JonB]

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

ui->spinBox->setValue(08246);
The code throws an error when I enter such a value

The code throws an error? At runtime? Don't you mean the compiler throws an error on this? 08246 as a C++ literal is octal, because of the leading 0, and then 8 is not a valid digit in base 8!

If you want to retain a leading 0, so it's not "really" "just" a number, that is harder (also in a QSpinBox if you changed to use that, though still doable). As it is, this is why @J-Hilk's code shows how to achieve it.

[wtimm]

if i use originalLength function i got use of undeclared identifier 'originalLength' error

[Pl45m4]

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

auto originalLength = ui->lineEdit->text().length();

@wtimm Do you have this in your code?

[JonB]

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

if i use originalLength function i got use of undeclared identifier 'originalLength' error

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

auto originalLength = ui->lineEdit->text().length();
ui->lineEdit->setText(QString::number(val).rightJustified(originalLength, '0'));

It's not a "function". So how did you get "undeclared identifier"?

[wtimm]

you are right it is not a function , thanks all of you for your help

[wtimm]

how can i see '0547' as default value when i run the project again

[JonB]

@wtimm
Well you need to save that value to some permanent storage to be able to retrieve it next time! Unless you are using a database in your application Qt's QSettings is the most convenient way.

[wtimm]

int v = settings.value(number(val),defaultValue).toInt();

I wrote such a code but it didn't work.
When I save the increased value, how can I make the increased value show as default when I open the project again?

[Pl45m4]

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

When I save the increased value, how can I make the increased value show as default when I open the project again?

Save the increased (always the current) value when you close your project?!

[JonB]

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

I wrote such a code but it didn't work.

Meaning what? Please don't just say "it didn't work" if you want people to understand enough to help. Your code shows reading back a value. How do we know what you saved where how? Did you look in the external INI file or Windows Registry to see what is there which has been saved?

When I save the increased value, how can I make the increased value show as default when I open the project again?

Read it back in somewhere at startup and set the widget's value from the previously saved.

[wtimm]

@Pl45m4 how can i save this , may i use QSettings or different class

[JonB]

@wtimm Already told you to save it via QSettings, there really isn't anything else to say....

[wtimm]

@JonB we have defined the variable val in the above answers (the value in the line edit)

Can we do it if we define val inside the setValue function or should we do it using another function?

void Widget::on_grabDataButton_clicked()
{
QSettings settings;
settings.setValue("val",1);
settings.value("val").toInt();
}

[Pl45m4]

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

void Widget::on_grabDataButton_clicked()
{
QSettings settings;
settings.setValue("val",1);
settings.value("val").toInt();
}

Dont know what this should do. Maybe you are using QSettings wrong.

To set value
settings.setValue("val", 42);

To read the value:
int val = settings.value("val").toInt();

And do whatever you like with val (set it to your line edit after you start your program)