Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. General talk
  3. Brainstorm
  4. Help sending data from dialog to main window
Forum Updated to NodeBB v4.3 + New Features

Help sending data from dialog to main window

Scheduled Pinned Locked Moved Unsolved Brainstorm
13 Posts 5 Posters 766 Views 2 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • J JonB
    22 Jan 2025, 09:56

    @Cantona
    Provide a public getter and a setter for the text in the line edit in the dialog (subclass QDialog). Include the dialog declaration via header file into main window, so it knows about it. Optionally set the value via setter to something (e.g. empty string) prior to invoking QDialog::exec(). Upon return from that, check result to see whether user went "OK" or "Cancel". If "OK" assign to variable in main window via getter in dialog.

    In other words, just use public setters & getters to access text value in dialog from main window.

    You could also use signal from dialog to pass username to slot in main window, but I don't see a need here, unless you prefer that to getter/setter. Getter/setter can be expanded more easily, e.g. if you decide to pass a password back as well as a username.

    If this is a "play" project you could just use QInputDialog::getText() to get a single string returned from a dialog instead. But that is limited to just that.

    C Offline
    C Offline
    Cantona
    wrote on 22 Jan 2025, 12:14 last edited by
    #4

    @JonB

    Please can you show a quick guide on how to use signals and slot for this

    J 1 Reply Last reply 22 Jan 2025, 12:51
    0
    • C Cantona
      22 Jan 2025, 12:14

      @JonB

      Please can you show a quick guide on how to use signals and slot for this

      J Offline
      J Offline
      JonB
      wrote on 22 Jan 2025, 12:51 last edited by JonB
      #5

      @Cantona Why, given that I said of signals/slots "but I don't see a need here"? Getter/setter is simpler and better here.

      C 1 Reply Last reply 22 Jan 2025, 13:04
      0
      • J JonB
        22 Jan 2025, 12:51

        @Cantona Why, given that I said of signals/slots "but I don't see a need here"? Getter/setter is simpler and better here.

        C Offline
        C Offline
        Cantona
        wrote on 22 Jan 2025, 13:04 last edited by
        #6

        @JonB

        I have never used getter/setter in qt so I don't know how to go about it

        J 1 Reply Last reply 22 Jan 2025, 13:34
        0
        • C Cantona
          22 Jan 2025, 13:04

          @JonB

          I have never used getter/setter in qt so I don't know how to go about it

          J Offline
          J Offline
          JonB
          wrote on 22 Jan 2025, 13:34 last edited by JonB
          #7

          @Cantona
          You have used it many times, Qt uses this pattern for all its class variables. It's just simple C++ (or Python):

          // .h file
          class UsernameDialog : public QDialog
          {
          public:
              const QString &username() const;    // "getter" for username
              void setUsername(const QString &username);    // "setter" for username, probably not used for this case
          }
          
          // .cpp file
          const QString &UsernameDialog::username() const
          {
              return ui->lineEdit.text();
          }
          void UsernameDialog::setUsername(const QString &username)
          {
              ui->lineEdit.setText(username);
          }
          
          // mainwindow cpp file
          QString username;
          UsernameDialog *usernameDialog = new UsernameDialog;
          if (usernameDialog->exec())
              username = usernameDialog->username();
          
          C 1 Reply Last reply 22 Jan 2025, 16:41
          1
          • J JonB
            22 Jan 2025, 13:34

            @Cantona
            You have used it many times, Qt uses this pattern for all its class variables. It's just simple C++ (or Python):

            // .h file
            class UsernameDialog : public QDialog
            {
            public:
                const QString &username() const;    // "getter" for username
                void setUsername(const QString &username);    // "setter" for username, probably not used for this case
            }
            
            // .cpp file
            const QString &UsernameDialog::username() const
            {
                return ui->lineEdit.text();
            }
            void UsernameDialog::setUsername(const QString &username)
            {
                ui->lineEdit.setText(username);
            }
            
            // mainwindow cpp file
            QString username;
            UsernameDialog *usernameDialog = new UsernameDialog;
            if (usernameDialog->exec())
                username = usernameDialog->username();
            
            C Offline
            C Offline
            Cantona
            wrote on 22 Jan 2025, 16:41 last edited by
            #8

            @JonB

            Sorry I couldn't get this to work

            1 Reply Last reply
            0
            • S Offline
              S Offline
              SGaist
              Lifetime Qt Champion
              wrote on 22 Jan 2025, 19:19 last edited by
              #9

              Hi,

              What exactly did not work now ?

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

              C 1 Reply Last reply 22 Jan 2025, 21:14
              0
              • S SGaist
                22 Jan 2025, 19:19

                Hi,

                What exactly did not work now ?

                C Offline
                C Offline
                Cantona
                wrote on 22 Jan 2025, 21:14 last edited by
                #10

                @SGaist

                Everything I guess. D variable username still is not getting any data assigned to it

                P 1 Reply Last reply 23 Jan 2025, 00:05
                0
                • C Cantona
                  22 Jan 2025, 21:14

                  @SGaist

                  Everything I guess. D variable username still is not getting any data assigned to it

                  P Offline
                  P Offline
                  Pl45m4
                  wrote on 23 Jan 2025, 00:05 last edited by
                  #11

                  @Cantona said in Help sending data from dialog to main window:

                  variable username still is not getting any data assigned to it

                  Unpleasant answer but no secret or surprise:
                  You need to know C++ if you want to get somewhere with Qt :)
                  Learn the basics of C++ and OOP and you will understand better and learn faster how to work with Qt.

                  @JonB said in Help sending data from dialog to main window:

                  // mainwindow cpp file
                  QString username;
                  UsernameDialog *usernameDialog = new UsernameDialog;
                  if (usernameDialog->exec())
                      username = usernameDialog->username();
                  

                  This answer by @JonB is basically everything you need to do to return your variable from your dialog and assign it to something within your QMainWindow class.


                  If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                  ~E. W. Dijkstra

                  1 Reply Last reply
                  2
                  • C Cantona
                    22 Jan 2025, 09:45

                    Hello everyone, am new to the forum.
                    Ok so I have two Windows in my project, main window and a dialog window called login. This login window just have a line edit called username and a push button called loginbtn. What I want is to have a QString variable called username in the main window that is equal to an empty string, so when I provide a username in the dialog window and click the login button, the text in the line edit get assigned to the empty username variable in the main window. Thank you.

                    alexjordan_nowA Offline
                    alexjordan_nowA Offline
                    alexjordan_now
                    wrote on 10 Mar 2025, 08:07 last edited by
                    #12

                    @Cantona You can achieve this by emitting a signal from the login dialog and connecting it to a slot in the main window. In LoginDialog, emit a signal like emit sendUsername(username); when the button is clicked. Then, in MainWindow, connect it with connect(loginDialog, &LoginDialog::sendUsername, this, &MainWindow::setUsername);.

                    Hope these steps help you out!

                    P 1 Reply Last reply 10 Mar 2025, 10:47
                    0
                    • alexjordan_nowA alexjordan_now
                      10 Mar 2025, 08:07

                      @Cantona You can achieve this by emitting a signal from the login dialog and connecting it to a slot in the main window. In LoginDialog, emit a signal like emit sendUsername(username); when the button is clicked. Then, in MainWindow, connect it with connect(loginDialog, &LoginDialog::sendUsername, this, &MainWindow::setUsername);.

                      Hope these steps help you out!

                      P Offline
                      P Offline
                      Pl45m4
                      wrote on 10 Mar 2025, 10:47 last edited by
                      #13

                      @alexjordan_now said in Help sending data from dialog to main window:

                      You can achieve this by emitting a signal from the login dialog and connecting it to a slot in the main window

                      That's one way that was also already mentioned before :)
                      Though I think if you want to return one value only, setting up a signal/slot connection is more "work" than just returning the value directly to the caller.


                      If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                      ~E. W. Dijkstra

                      1 Reply Last reply
                      1

                      • Login

                      • Login or register to search.
                      • First post
                        Last post
                      0
                      • Categories
                      • Recent
                      • Tags
                      • Popular
                      • Users
                      • Groups
                      • Search
                      • Get Qt Extensions
                      • Unsolved