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

[wtimm]

can you help me please?

[jsulm]

@wtimm Connect a slot to https://doc.qt.io/qt-6/qabstractbutton.html#clicked signal ofrom your check box. In that slot get the value of the line edit using https://doc.qt.io/qt-6/qlineedit.html#text-prop. Convert that text to number using https://doc.qt.io/qt-6/qstring.html#toInt. Increment this number and set it again in your text edit using https://doc.qt.io/qt-6/qstring.html#number-1 and https://doc.qt.io/qt-6/qlineedit.html#text-prop

If your line edit only accepts numbers you should use https://doc.qt.io/qt-6/qspinbox.html instead.

[wtimm]

I want it to increase from U12C5 to U12C6 but when I write the code it returns 1. Is it possible to do what I want in qt

[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