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Undefined reference to external variable

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  • S Offline
    S Offline
    Spike89
    wrote on last edited by
    #1

    I declared here an extern variable:
    open.h
    @
    extern QString filename;
    @
    I defined here: open.cpp
    @
    void open::openfile()
    {
    QString filename=QFileDialog::getOpenFileName(
    0,
    QObject::tr("Open File"),
    ("C://"),
    ("BITMAP(*.bmp)")
    );
    QFile file(filename);
    file.open(QIODevice::ReadOnly);
    QByteArray ba=file.readAll();

    }
    

    @
    And i want to use here like this:
    mainwindow.cpp
    @
    ui->lineEdit->setText(filename);
    @
    But i got this error: undefined refernce to 'filename'
    What am i doing wrong?

    1 Reply Last reply
    0
    • JKSHJ Online
      JKSHJ Online
      JKSH
      Moderators
      wrote on last edited by
      #2

      Hi,

      in your code, filename is a local variable inside your openfile() function. For it to be an extern variable, you need to define it outside all functions:

      @
      QString filename;

      void open::openfile()
      {
      filename = ...
      @

      However, consider redesigning your program. Minimize your use extern/global variables to make your code more maintainable -- make filename a member variable of an object instead.

      Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

      1 Reply Last reply
      0

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