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()); });