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Serializing a widget

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  • 6 Offline
    6 Offline
    6thC
    wrote on 16 Aug 2018, 00:46 last edited by
    #9

    Well, first I'd say:
    General advice is always use prepared statements.
    Prepare: https://stackoverflow.com/questions/5609245/qsqlquery-prepared-statements-proper-usage

    More general advice is figure out the actual query you sent the engine by firing a verbatim copy of the query generated in your application directly @ the engine without the application.

    So, how I see it:

    • Determine the actual statement
    • run it at the engine (using with command line or query / db engine tools and see the response - independent from your application anyhow).
    • Witness the engine response as a result of your statement (I'm expecting a syntax error as it seems you are too)
    • This will lead you to the reasons what is not being correctly done in your application.
    • Fix the application statement
    • Try again

    I suspect it would be a parsing error as you're playing with the single quotes but cannot say. I also won't troubleshoot what seems just syntax/parsing... that's for you to determine / observe.

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    • E Offline
      E Offline
      EL-jos
      wrote on 17 Aug 2018, 23:00 last edited by
      #10

      Hey, family,

      After a lot of testing, I understood that my database and my amis table are created but except that the amis table contains no columns so no fields.
      I tried to add the plugin qsqlited.dll and qsqlmysqld.dll since I compiled in debug mode but my amis table is still empty so no amis.
      Here's my code:

       QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
          db.setDatabaseName("base_de_donnees2.db");
          db.open();
          if(!db.isOpen())
              qDebug() << "ERREUR d'ouverture de la base de données; cause: " << db.lastError().text();
          QSqlQuery q;
          q.exec("CREATE TABLE IF NOT EXISTS amis (id INTEGER PRIMARY KEY AUTOINCREMENT, nom TEXT NOT NULL, photo BLOB NOT NULL) ");
      
          QSqlQuery q2;
          q2.prepare("INSERT INTO amis (id,nom,photo) VALUES (:id,:nom,:photo) ");
      
          int identifiant = 1;
          QString pseudo("EL-chrino");
          QFile fichier(QFileDialog::getOpenFileName());
          fichier.open(QIODevice::ReadOnly);
          QByteArray byte;
          if(!fichier.isOpen())
              qDebug() << "Echec d'ouverture du fichier";
          byte = fichier.readAll();
      
          q2.bindValue(":id",identifiant);
          q2.bindValue(":nom",pseudo);
          q2.bindValue(":photo",byte);
      
          if(!q2.exec())
              qDebug() << "ERREUR lors de l'exécution de la requête; cause: " << q2.lastError().text();
      
      

      Note that I have never used databases with Qt so I don't know how it works, please tell me what I need to do to use databases with Qt as it will be very important for my chatt software.
      Thank you in advance

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      0
      • E Offline
        E Offline
        EL-jos
        wrote on 18 Aug 2018, 12:49 last edited by
        #11

        I found in a forum, they say you need to recompile Qt and SQL Drive but it doesn't explain how to do it.

        Please if there is someone who knows how to make it watch you manifest

        M 1 Reply Last reply 18 Aug 2018, 13:24
        0
        • E EL-jos
          18 Aug 2018, 12:49

          I found in a forum, they say you need to recompile Qt and SQL Drive but it doesn't explain how to do it.

          Please if there is someone who knows how to make it watch you manifest

          M Offline
          M Offline
          mrjj
          Lifetime Qt Champion
          wrote on 18 Aug 2018, 13:24 last edited by
          #12

          @EL-jos
          Hi
          For QSQLITE
          you need to compile nothing or add any libraries.
          just
          QT += sql
          in your .pro file

          1 Reply Last reply
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          • E Offline
            E Offline
            EL-jos
            wrote on 22 Aug 2018, 04:11 last edited by
            #13

            Thank you very much for your advice, but I have two questions;
            first how to update a QscrollArea that already contains elements beforehand?
            and the second is how to make a message waiting list like this if a client "A" has just logged out and another client "B" sends him a message, that the message is in a list to wait for the client "A" to read it.
            like whatsapp or facebook notification when someone sends us a message while we're away, the message is kept until we read it?

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            0
            • S Offline
              S Offline
              SGaist
              Lifetime Qt Champion
              wrote on 22 Aug 2018, 19:16 last edited by
              #14

              Hi,

              You just append new widgets to the layout that already contains the others.

              As for the messages, if you are thinking on how it’s working on mobile platform, you’ll have several things to take into consideration.

              So some questions for you:

              • On what platform(s) is your application going to run ?
              • How are the client going to talk to each other ?

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

              1 Reply Last reply
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              • E Offline
                E Offline
                EL-jos
                wrote on 24 Aug 2018, 19:24 last edited by
                #15

                Regarding the update of my scroollArea, I don't want to add elements but rather delete completely what it already contains.

                then for the messages I want my application to run all over the platform but first on Pc using the windows operating system.

                for my clients, I use TCP/ip protocol so with QTcpSocket class

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                0
                • S Offline
                  S Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on 24 Aug 2018, 19:58 last edited by
                  #16

                  The most elegant would likely be to have the messages stored in a model and then have a custom QStyledItemDelegate to paint whatever you want.

                  Again: how are you client talking to each other ? Through a central server ? How do they know each other ?

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

                  1 Reply Last reply
                  0
                  • E Offline
                    E Offline
                    EL-jos
                    wrote on 24 Aug 2018, 23:14 last edited by
                    #17

                    Hi,

                    Yes I use a server for the dialog between client, this means that if a client'A' sends a message to client'B', it will first go through the server then the server will send me to the destination so client'B'.

                    1 Reply Last reply
                    0
                    • E Offline
                      E Offline
                      EL-jos
                      wrote on 27 Aug 2018, 17:20 last edited by
                      #18

                      please someone has an idea.

                      M 1 Reply Last reply 27 Aug 2018, 17:23
                      0
                      • E EL-jos
                        27 Aug 2018, 17:20

                        please someone has an idea.

                        M Offline
                        M Offline
                        mrjj
                        Lifetime Qt Champion
                        wrote on 27 Aug 2018, 17:23 last edited by
                        #19

                        @EL-jos
                        About ?

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                        0
                        • E Offline
                          E Offline
                          EL-jos
                          wrote on 28 Aug 2018, 01:26 last edited by
                          #20

                          In fact I want to make sure that if we send a message to a client that is not connected, that this client sees the message that has been sent as soon as it is connected.

                          J 1 Reply Last reply 28 Aug 2018, 04:21
                          0
                          • E EL-jos
                            28 Aug 2018, 01:26

                            In fact I want to make sure that if we send a message to a client that is not connected, that this client sees the message that has been sent as soon as it is connected.

                            J Offline
                            J Offline
                            JKSH
                            Moderators
                            wrote on 28 Aug 2018, 04:21 last edited by JKSH
                            #21

                            @EL-jos said in Serializing a widget:

                            I want to make sure that if we send a message to a client that is not connected, that this client sees the message that has been sent as soon as it is connected.

                            Then the central server must store the message. When the client comes online, the server can deliver the message to the client.

                            Note: This concept is about communications architecture. This is not related to widgets at all.

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

                            1 Reply Last reply
                            2
                            • E Offline
                              E Offline
                              EL-jos
                              wrote on 28 Aug 2018, 13:35 last edited by
                              #22

                              ahhhhh yes you're right, so I can store the message in a database at the server level then as soon as the concerned client is connected the server will be able to restore the message then send it to the client, thank you very much.

                              then a second unresolved problem so far;
                              here I have a scrollArea which first contains many widgets of different type, so I want to delete either empty all these widgets and left the scrollArea blank so without element,
                              how do I do that?

                              J 1 Reply Last reply 28 Aug 2018, 13:41
                              0
                              • E EL-jos
                                28 Aug 2018, 13:35

                                ahhhhh yes you're right, so I can store the message in a database at the server level then as soon as the concerned client is connected the server will be able to restore the message then send it to the client, thank you very much.

                                then a second unresolved problem so far;
                                here I have a scrollArea which first contains many widgets of different type, so I want to delete either empty all these widgets and left the scrollArea blank so without element,
                                how do I do that?

                                J Offline
                                J Offline
                                JKSH
                                Moderators
                                wrote on 28 Aug 2018, 13:41 last edited by
                                #23

                                @EL-jos said in Serializing a widget:

                                here I have a scrollArea which first contains many widgets of different type, so I want to delete either empty all these widgets and left the scrollArea blank so without element,
                                how do I do that?

                                Have a read through http://doc.qt.io/qt-5/qscrollarea.html . Do you see anything that might do what you want?

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

                                1 Reply Last reply
                                0
                                • E Offline
                                  E Offline
                                  EL-jos
                                  wrote on 28 Aug 2018, 14:52 last edited by
                                  #24

                                  I just read and reread the Qt documentation for the QScrollArea class or even its mother classes but I can't find the solution to my problem because there is not a function that allows to remove all widgets contained in a scrollAreea

                                  M 1 Reply Last reply 28 Aug 2018, 14:54
                                  0
                                  • E EL-jos
                                    28 Aug 2018, 14:52

                                    I just read and reread the Qt documentation for the QScrollArea class or even its mother classes but I can't find the solution to my problem because there is not a function that allows to remove all widgets contained in a scrollAreea

                                    M Offline
                                    M Offline
                                    mrjj
                                    Lifetime Qt Champion
                                    wrote on 28 Aug 2018, 14:54 last edited by
                                    #25

                                    @EL-jos
                                    Hi
                                    Are the widgets not in a layout ?
                                    You can clear layout with

                                    void clearLayout(QLayout *layout)
                                        QLayoutItem *item;
                                        while((item = layout->takeAt(0))) {
                                            if (item->layout()) {
                                                clearLayout(item->layout());
                                                delete item->layout();
                                            }
                                            if (item->widget()) {
                                                delete item->widget();
                                            }
                                            delete item;
                                        }
                                    }
                                    
                                    1 Reply Last reply
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                                    • E Offline
                                      E Offline
                                      EL-jos
                                      wrote on 28 Aug 2018, 16:45 last edited by
                                      #26

                                      Thank you for your code.
                                      theoretically it works but not in practice according to my example, here is a little project I created to test your code:

                                      [7_1535474695539_fenetre1.cpp](Uploading 100%) [6_1535474695538_fenetre1.h](Uploading 100%) [5_1535474695538_fenetresecond.cpp](Uploading 100%) [4_1535474695537_fenetresecond.h](Uploading 100%) [3_1535474695537_fenetresecond.ui](Uploading 100%) [2_1535474695537_main.cpp](Uploading 100%) [1_1535474695535_Oc.pro](Uploading 100%) [0_1535474695483_Oc.pro.user](Uploading 100%)

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                                      • E Offline
                                        E Offline
                                        EL-jos
                                        wrote on 28 Aug 2018, 16:56 last edited by
                                        #27

                                        sorry I can't send my project on topic, send me your E-mail address so I can send it to you by E-mail

                                        M 1 Reply Last reply 28 Aug 2018, 17:18
                                        0
                                        • E EL-jos
                                          28 Aug 2018, 16:56

                                          sorry I can't send my project on topic, send me your E-mail address so I can send it to you by E-mail

                                          M Offline
                                          M Offline
                                          mrjj
                                          Lifetime Qt Champion
                                          wrote on 28 Aug 2018, 17:18 last edited by
                                          #28

                                          @EL-jos
                                          Sorry i dont have email i use for Qt forum.
                                          You can use dropbox or google drive.
                                          Are you sure u give it the correct layout ?
                                          Im sure code works so maybe its other layout u clear that u think.
                                          also use the debugger to see what happens.

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