Qt - I want to use the QComboBox after the return/enter is pressed.

[developer_96]

I have the following problem:

I'm using the QComboBox of QT to select a path by a Drop & Down. It is working fine after I choose one of the list, the path is automatically update. But now if I want to edit the Path manually by type in a path, I get immediately a warning. So I know that this is happening cause of the argument:

connect(ui.leftBox, &QComboBox::currentTextChanged, this, &MainCom::updatepath);

So always if I'm going to change the path, for example by changing only one letter or select it by Drop & Down the "currentTextChanged" calls the function 'updatepath'
So what I want to achieve is that if I'm going to select a path the function should be called normally. But if I'm going to type in a new path or editing the path manually I want that the function will be called after type "return".

I hope you can help.

[JonB]

@developer_96
Try QComboBox::editTextChanged instead. If that behaves the same, I guess you'll need to pick up QLineEdit *QComboBox::lineEdit() and slot onto QLineEdit::editingFinished() for that.

[developer_96]

@JonB i can not use the QLineEdit in my connect.

[jsulm]

@developer_96 said in Qt - I want to use the QComboBox after the return/enter is pressed.:

i can not use the QLineEdit in my connect.

Why not? you can get the pointer to line edit from your combo box using QLineEdit *QComboBox::lineEdit() as @JonB pointed out.

[developer_96]

@jsulm don't know. I tried to use

QLineEdit::editingFinished()

in my connect function like:

connect(ui.leftBox, &QLineEdit::editingFinished, this, &MainCom::updatepath);

but it does not work.

[mrjj]

@developer_96

hi
should that not be
connect(ui.leftBox->lineEdit(), &QLineEdit::editingFinished, this, &MainCom::updatepath);

[jsulm]

@developer_96 said in Qt - I want to use the QComboBox after the return/enter is pressed.:

but it does not work

As mentioned already: you need to get the pointer to the line edit using QLineEdit *QComboBox::lineEdit() and use that pointer in the connect.

[JonB]

@developer_96

I guess you'll need to pick up QLineEdit *QComboBox::lineEdit() and slot onto QLineEdit::editingFinished() for that.

[developer_96]

@jsulm how?
@mrjj i tried your code. It say "The expression must be of a class type."

Regards

[JonB]

@developer_96
You have a QComboBox. I gave you the method you need to access its QLineEdit. connect() the line edit's QLineEdit::editingFinished signal to the desired slot.

[developer_96]

@JonB i try to acces it by using

connect(ui.leftBox, &QLineEdit::editingFinished, this, &MainCom::updatepath);

and

 connect(ui.leftBox->lineEdit(), &QLineEdit::editingFinished, this, &MainCom::updatepath);

but it does not work.
Thank you for the help.

[JonB]

@developer_96
The first one will generate a compiler-time error.

The second one is correct. What "does not work"? have you tried putting a qDebug() in your &MainCom::updatepath() method, does it get hit?

[developer_96]

@JonB it says "An incomplete type is not allowed" for &QLineEdit::editingFinished.

[JonB]

@developer_96
Put #include <QLineEdit> at the head of your source (.cpp) file.

[developer_96]

@JonB thank you. yeah i know but i removed it cause i get this problem after i put in and try to debug:

[jsulm]

@developer_96 Please show the relevant code.
Does your updatepath() slot have any parameters?

[developer_96]

@jsulm
Connect:

connect(ui.leftBox->lineEdit(), &QLineEdit::editingFinished, this, &MainCom::updatepath);

Updaatepath:

void MainCom::updatepath(const QString& path)

[Christian Ehrlicher]

And where do you expect does const QString& path should come from when the signal does not have a parameter?

[jsulm]

@developer_96 said in Qt - I want to use the QComboBox after the return/enter is pressed.:

QLineEdit::editingFinished

Has no parameter, so you can't connect it with a slot which expects a parameter. That's exactly what the first error message is saying.

[JonB]

@developer_96
One/the best way of doing what you want --- pass your own extra parameter to slot --- is to learn to use C++ lambdas here:

connect(ui.leftBox->lineEdit(), &QLineEdit::editingFinished,
        this, [this]() { this->updatepath(this->ui.leftBox->lineEdit()->text()); });
// or next line does exactly the same thing, depends which you find clearer
connect(ui.leftBox->lineEdit(), &QLineEdit::editingFinished,
        this, [this]() { updatepath(ui.leftBox->lineEdit()->text()); });

[developer_96]

@JonB @Christian-Ehrlicher @jsulm thank you very much for the answers. I did it now. The function will be called after i type "return". But now if i chose one of the drop & down the programm wants from to type "return" again. My Idea was to type "return" when i manually type a path. When i'm going to select one path of the drop & down i want to update it immediately.

Regards

[JonB]

@developer_96
So far you have dealt with the user editing the text. For choosing an item from the dropdown, I think you have to also connect the QComboBox::currentIndexChanged() to your slot.

P.S.
It's not your fault that QComboBox does not seem to define one signal for "finished editing, either by typing all into the line edit or selecting an item from the dropdown". It would have been nicer if it did.

[developer_96]

@JonB so its possible to connect two signals to one slot?

[JonB]

@developer_96
Absolutely! Many-to-many relationship: as many signals as you like connected to same slot and/or as many slots as you like connected to any signal.

[developer_96]

Hey @JonB thank you. I solved it finally !