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Thread: How to call member function from int main()

  1. #1
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    Default How to call member function from int main()

    Hi I am a beginner in programming in C++ with Qt 4, I must write a program to ask the user for a Temperature in Celcius using QInputDialog, I wrote the header with the class and .cpp wiht the fucnction file, but are battling calling the function in the main.cpp. Please advice me on where I went wrong:

    Header:

    #ifndef INPUTDIALOG_H
    #define INPUTDIALOG_H

    class InputDialog
    {
    public:
    ~InputDialog();
    void getTemp();
    private slots:
    private:
    };
    #endif // INPUTDIALOG_H

    InputDialog.cpp:

    #include "inputdialog.h"
    #include <QWidget>
    #include <QInputDialog>
    #include <QMessageBox>
    #include <QObject>
    #include <QLabel>


    InputDialog::~InputDialog()
    {

    }

    void InputDialog::getTemp()
    {
    bool (ok);
    int *temperature = QInputDialog::getInt(temperature,tr("Enter a Temperature in Celsius"),tr("Celsius"),0,-30,100,1,&ok);
    if (ok)
    integerLable->setText(tr("%1%").arg(temperature));
    }

    Main.cpp:

    #include <QtGui/QApplication>
    #include "inputdialog.h"

    int main(int argc, char *argv[])
    {
    QApplication app(argc, argv);

    InputDialog.getTemp();

    return app.exec();
    }

  2. #2
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    Default Re: How to call member function from int main()

    Hi,

    Roughly said, in a GUI application, you can't show anything to the user before your app.exec(). Create a dialog and call show() before the app.exec(). The dialog will be shown when app.exec() is called.

    In the dialog code, you can write stuff (create a button and attach a slot to its clicked event) to show the input dialog.

    See http://doc.trolltech.com/3.0/t1.html for a (very old) example.

    Best regards,
    Marc

  3. #3
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    Default Re: How to call member function from int main()

    InputDialog dialog;
    dialog.getTemp();

    you need to learn c++ before you can use Qt.
    If you have a problem, CUT and PASTE your code. Do not retype or simplify it. Give a COMPLETE and COMPILABLE example of your problem. Otherwise we are all guessing the problem from a fabrication where relevant details are often missing.

  4. #4
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    Default Re: How to call member function from int main()

    Quote Originally Posted by marcvanriet View Post
    Roughly said, in a GUI application, you can't show anything to the user before your app.exec(). Create a dialog and call show() before the app.exec(). The dialog will be shown when app.exec() is called.
    Actually in this situation it would work provided the syntax was correct. QInputDialog launches a modal dialog, just like you would have called QDialog::exec() which spins an event loop and is able to show the dialog.
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

    Please ask Qt related questions on the forum and not using private messages or visitor messages.


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