qt5 designer, using fileopen, displaying file path in lineedit, is there an issue doing it this way?

Question

just started using qt, looked through docs, google, examples, etc.. trying to find simple examples(working mind you) that showed how to do (imho) simple things, by themselves. well i stumbled upon my answer and i was wondering if this approach would cause an issue later as the code becomes more complex. there are more includes than needed for this example, but this is direct from working code. mainwindow.h: i added

private slots:
    void vpkButton_clicked();

and after Ui::MainWindow *ui; i added QLineEdit *vpkPathTxt; in mainwindow.cpp: after

    ui->setupUi(this);

i added

    connect( this->ui->vpkButton, SIGNAL( clicked() ), this, SLOT(vpkButton_clicked()) );

to connect my ui button to the proper slot, the issue was getting the string from vpkButton_clicked() to display in the line edit i made in the designer, what ended up working for me was adding this next:

    vpkPathTxt = this->ui->vpkPathTxt;

the function in my main.cpp became very easy: (QString declarations at top outside voids)

void MainWindow::vpkButton_clicked()
{
    vpkName = QFileDialog::getOpenFileName(this,
        tr("Open VPK File"), "~/", tr("VPK Files (*_dir.vpk)"));
    vpkPathTxt->setText(vpkName);
    qDebug() << vpkName;
}

the reason i am ask is because it seems a little too easy to be reliable, and the fact that i havent seen it done like this, any input welcome thankyou

Why do you use another variable `vpkPathTxt` pointing to your `ui->vpkPathTxt`? Simply to save some typing? The idea behind the `ui` pointer is that it encapsulates all UI elements so it doesn't "interfer" with other variables needed for logic stuff in your class. Also, the `this->` is optional; I'd leave it out. — leemes, Dec 11 '13 at 19:52
That's because `vpkPathTxt` is an uninitialized pointer you use in other statements. Replace them with `ui->vpkPathTxt` and remove the variable in your header file. If I understood you correctly you have such a variable in the header below `Ui::MainWindow *ui`. — leemes, Dec 11 '13 at 20:06
without "vpkPathTxt = this->ui->vpkPathTxt;" the app simply disapears, when i choose the file whose path will be displayed in it, using "ui->vpkPathTxt.setText(vpkName);" fails miserably,maybe because i dont have a proper connect going on/ — angjminer, Dec 11 '13 at 20:06
Ok the last thing you described is strange. Try the following: remove the connect and rename your slot to **exactly** `on_vpkButton_clicked()`; this will connect it to the signal *automatically* for you. Instead of writing the name of the slot by hand you can right click in the designer on the widget, select "go to slot", choose the slot and it will be created accordingly. — leemes, Dec 11 '13 at 20:08
you sir are awesome!!! thankyou so much for taking the time to answer me. — angjminer, Dec 11 '13 at 20:18

score 0 · Accepted Answer · answered Dec 11 '13 at 20:15

One problem with your slot is that you don't consider the case where the user discards the "open file" dialog. In this case, the function QFileDialog::getOpenFileName returns a null QString, so you should only proceed with your logic if the return value was not a null string:

if (!vpkName.isNull()) {
    ...
}

The second problem is as follows and I made some assumptions since I don't see your full code:

I guess you want to load a file using the file name the user has chosen in the dialog. But you set the file name in the line edit too, which the user can edit by hand. I also guess that the actual file loading happens in a different step (i.e. after clicking another button), so after the user has edited the file name by hand in the line edit it won't be the same than in your local variable vpkName.

When loading the file I'd read the contents of the line edit instead of the variable vpkName so the edit made by hand will be respected.

A different method is to also watch for editing of the line edit and reflect the changes in your variable too. Then it will be ok to read the variable instead of the line edit when loading the file later on.

ThankYou, adding the slot with the right click worked great(it also put the code on the right page). may you have awesome dreams tonight. :) — angjminer, Dec 11 '13 at 20:27

qt5 designer, using fileopen, displaying file path in lineedit, is there an issue doing it this way?

1 Answers1