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QObject::connect: Cannot queue arguments of type

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  • M micha_eleric

    @ChrisW67

    int id = qRegisterMetaType< QList<float> >();
    

    is in both classes that use QList<float>, and still get the error

    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by
    #8

    @micha_eleric
    First you should get your code compiling and running correctly as per @ChrisW67. You will need to use the Q_OBJECT macro., and you should use connect() syntax shown, not SIGNAL/SLOT() macros.

    But you may end up needing to reconsider your array/list arguments to the signal/slot. I assume you are signalling across threads. Qt will copy any arguments. If your array is "large" or if you intend to update the array in the slot (not just read from it) you may/will need to reconsider.

    M 1 Reply Last reply
    2
    • C ChrisW67

      @HaoTian Indeed, you are correct. This, for example, works:

      #include <QCoreApplication>
      #include <QObject>
      #include <QList>
      #include <QDebug>
      #include <QTimer>
      
      class Object: public QObject {
              Q_OBJECT
      public:
              Object(QObject *p = nullptr): QObject(p) {
                      QTimer::singleShot(
                                      5000, this,
                                      [this]() { emit send(QList<float> { 0, 1.2, 2.3, 3.4 } ); }
                      );
              };
              ~Object() { }
      
      public slots:
              void receive(QList<float> list) {
                      qDebug() << list;
              }
      signals:
              void send(QList<float> list);
      
      };
      
      
      int main(int argc, char **argv) {
              QCoreApplication app(argc, argv);
      
              Object *a = new Object(qApp);
              Object *b = new Object(qApp);
              QObject::connect(a, &Object::send, b, &Object::receive);
      
              return app.exec();
      }
      
      #include "main.moc"
      

      So, @micha_eleric, what are you not telling us? Are there threads involved? Can you modify the example above to fail in the same way?

      SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #9

      @ChrisW67 said in QObject::connect: Cannot queue arguments of type:

      @HaoTian Indeed, you are correct. This, for example, works:

      #include <QCoreApplication>
      #include <QObject>
      #include <QList>
      #include <QDebug>
      #include <QTimer>
      
      class Object: public QObject {
              Q_OBJECT
      public:
              Object(QObject *p = nullptr): QObject(p) {
                      QTimer::singleShot(
                                      5000, this,
                                      [this]() { emit send(QList<float> { 0, 1.2, 2.3, 3.4 } ); }
                      );
              };
              ~Object() { }
      
      public slots:
              void receive(QList<float> list) {
                      qDebug() << list;
              }
      signals:
              void send(QList<float> list);
      
      };
      
      
      int main(int argc, char **argv) {
              QCoreApplication app(argc, argv);
      
              Object *a = new Object(qApp);
              Object *b = new Object(qApp);
              QObject::connect(a, &Object::send, b, &Object::receive);
      
              return app.exec();
      }
      
      #include "main.moc"
      

      So, @micha_eleric, what are you not telling us? Are there threads involved? Can you modify the example above to fail in the same way?

      If I may just add something: use const references, this will avoid potentially expensive copies when possible.

      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
      • H HaoTian

        @micha_eleric No no, it's not necessary to register anything. because QList is automatically registered by Qt and basic types do not need to be registered either.

        M Offline
        M Offline
        micha_eleric
        wrote on last edited by
        #10

        @HaoTian which is why I wonder why it gives this error when it runs

        QObject::connect: Cannot queue arguments of type 'QList<float>'
        (Make sure 'QList<float>' is registered using qRegisterMetaType().)
        
        1 Reply Last reply
        0
        • C ChrisW67

          @HaoTian Indeed, you are correct. This, for example, works:

          #include <QCoreApplication>
          #include <QObject>
          #include <QList>
          #include <QDebug>
          #include <QTimer>
          
          class Object: public QObject {
                  Q_OBJECT
          public:
                  Object(QObject *p = nullptr): QObject(p) {
                          QTimer::singleShot(
                                          5000, this,
                                          [this]() { emit send(QList<float> { 0, 1.2, 2.3, 3.4 } ); }
                          );
                  };
                  ~Object() { }
          
          public slots:
                  void receive(QList<float> list) {
                          qDebug() << list;
                  }
          signals:
                  void send(QList<float> list);
          
          };
          
          
          int main(int argc, char **argv) {
                  QCoreApplication app(argc, argv);
          
                  Object *a = new Object(qApp);
                  Object *b = new Object(qApp);
                  QObject::connect(a, &Object::send, b, &Object::receive);
          
                  return app.exec();
          }
          
          #include "main.moc"
          

          So, @micha_eleric, what are you not telling us? Are there threads involved? Can you modify the example above to fail in the same way?

          M Offline
          M Offline
          micha_eleric
          wrote on last edited by
          #11

          @ChrisW67 it is with threads, and the only place I have seen

          QObject::connect: Cannot queue arguments of type 'QList<float>'
          (Make sure 'QList<float>' is registered using qRegisterMetaType().)
          

          show while running

          1 Reply Last reply
          0
          • JonBJ JonB

            @micha_eleric
            First you should get your code compiling and running correctly as per @ChrisW67. You will need to use the Q_OBJECT macro., and you should use connect() syntax shown, not SIGNAL/SLOT() macros.

            But you may end up needing to reconsider your array/list arguments to the signal/slot. I assume you are signalling across threads. Qt will copy any arguments. If your array is "large" or if you intend to update the array in the slot (not just read from it) you may/will need to reconsider.

            M Offline
            M Offline
            micha_eleric
            wrote on last edited by
            #12

            @JonB said in QObject::connect: Cannot queue arguments of type:

            @micha_eleric
            First you should get your code compiling and running correctly as per @ChrisW67. You will need to use the Q_OBJECT macro., and you should use connect() syntax shown, not SIGNAL/SLOT() macros.

            But you may end up needing to reconsider your array/list arguments to the signal/slot. I assume you are signalling across threads. Qt will copy any arguments. If your array is "large" or if you intend to update the array in the slot (not just read from it) you may/will need to reconsider.

            it compiles and runs, but

            QObject::connect: Cannot queue arguments of type 'QList<float>'
            (Make sure 'QList<float>' is registered using qRegisterMetaType().)
            

            shows on console while running

            SGaistS 1 Reply Last reply
            0
            • M micha_eleric

              @JonB said in QObject::connect: Cannot queue arguments of type:

              @micha_eleric
              First you should get your code compiling and running correctly as per @ChrisW67. You will need to use the Q_OBJECT macro., and you should use connect() syntax shown, not SIGNAL/SLOT() macros.

              But you may end up needing to reconsider your array/list arguments to the signal/slot. I assume you are signalling across threads. Qt will copy any arguments. If your array is "large" or if you intend to update the array in the slot (not just read from it) you may/will need to reconsider.

              it compiles and runs, but

              QObject::connect: Cannot queue arguments of type 'QList<float>'
              (Make sure 'QList<float>' is registered using qRegisterMetaType().)
              

              shows on console while running

              SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #13

              @micha_eleric Which version of Qt are you running ?

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

              M 1 Reply Last reply
              0
              • SGaistS SGaist

                @micha_eleric Which version of Qt are you running ?

                M Offline
                M Offline
                micha_eleric
                wrote on last edited by
                #14

                @SGaist said in QObject::connect: Cannot queue arguments of type:

                @micha_eleric Which version of Qt are you running ?

                been asked this before, and still no clue how to find out. All I can find is the version of the editor.

                C 1 Reply Last reply
                0
                • M micha_eleric

                  @SGaist said in QObject::connect: Cannot queue arguments of type:

                  @micha_eleric Which version of Qt are you running ?

                  been asked this before, and still no clue how to find out. All I can find is the version of the editor.

                  C Offline
                  C Offline
                  CPPUIX
                  wrote on last edited by
                  #15

                  @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                  how to find out

                  Which version of Qt am I using? How do I find out?

                  M 1 Reply Last reply
                  0
                  • C CPPUIX

                    @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                    how to find out

                    Which version of Qt am I using? How do I find out?

                    M Offline
                    M Offline
                    micha_eleric
                    wrote on last edited by
                    #16

                    @Abderrahmene_Rayene said in QObject::connect: Cannot queue arguments of type:

                    @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                    how to find out

                    Which version of Qt am I using? How do I find out?

                    instructions do not work for my version of QT Create, and once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                    JKSHJ 1 Reply Last reply
                    0
                    • M micha_eleric

                      @Abderrahmene_Rayene said in QObject::connect: Cannot queue arguments of type:

                      @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                      how to find out

                      Which version of Qt am I using? How do I find out?

                      instructions do not work for my version of QT Create, and once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                      JKSHJ Offline
                      JKSHJ Offline
                      JKSH
                      Moderators
                      wrote on last edited by
                      #17

                      @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                      once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                      That sounds very strange.

                      What do you see when you try Step #2 in the instructions?

                      M 1 Reply Last reply
                      0
                      • JKSHJ JKSH

                        @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                        once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                        That sounds very strange.

                        What do you see when you try Step #2 in the instructions?

                        M Offline
                        M Offline
                        micha_eleric
                        wrote on last edited by
                        #18

                        @JKSH said in QObject::connect: Cannot queue arguments of type:

                        @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                        once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                        That sounds very strange.

                        What do you see when you try Step #2 in the instructions?

                        lol, second step also gave no version, but can find editor version elsewhere
                        Qt Creator 6.0.2
                        Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                        Pl45m4P C 2 Replies Last reply
                        0
                        • M micha_eleric

                          @JKSH said in QObject::connect: Cannot queue arguments of type:

                          @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                          once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                          That sounds very strange.

                          What do you see when you try Step #2 in the instructions?

                          lol, second step also gave no version, but can find editor version elsewhere
                          Qt Creator 6.0.2
                          Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                          Pl45m4P Online
                          Pl45m4P Online
                          Pl45m4
                          wrote on last edited by Pl45m4
                          #19

                          @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                          Qt Creator 6.0.2
                          Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                          This is meaningless. It's the Qt version which was used to build your QtCreator version.

                          How are your build folders named? In some case they are named by default like:
                          build_<Projectname>_<QtX_X_X>_<Compiler>_<Architecture>

                          There you also can find out what Qt version you are using


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

                          ~E. W. Dijkstra

                          M 1 Reply Last reply
                          0
                          • Pl45m4P Pl45m4

                            @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                            Qt Creator 6.0.2
                            Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                            This is meaningless. It's the Qt version which was used to build your QtCreator version.

                            How are your build folders named? In some case they are named by default like:
                            build_<Projectname>_<QtX_X_X>_<Compiler>_<Architecture>

                            There you also can find out what Qt version you are using

                            M Offline
                            M Offline
                            micha_eleric
                            wrote on last edited by
                            #20

                            @Pl45m4 said in QObject::connect: Cannot queue arguments of type:

                            @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                            Qt Creator 6.0.2
                            Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                            This is meaningless. It's the Qt version which was used to build your QtCreator version.

                            How are your build folders named? In some case they are named by default like:
                            build_<Projectname>_<QtX_X_X>_<Compiler>_<Architecture>

                            There you also can find out what Qt version you are using

                            again nothing of use, "build-GraphicsView-Desktop-Debug"

                            M JKSHJ 2 Replies Last reply
                            0
                            • M micha_eleric

                              @Pl45m4 said in QObject::connect: Cannot queue arguments of type:

                              @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                              Qt Creator 6.0.2
                              Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                              This is meaningless. It's the Qt version which was used to build your QtCreator version.

                              How are your build folders named? In some case they are named by default like:
                              build_<Projectname>_<QtX_X_X>_<Compiler>_<Architecture>

                              There you also can find out what Qt version you are using

                              again nothing of use, "build-GraphicsView-Desktop-Debug"

                              M Offline
                              M Offline
                              micha_eleric
                              wrote on last edited by
                              #21

                              @micha_eleric well, after pecking around, i found:
                              Qt 4.8.7 in PATH (qt4) /usr/lib/x86_64-linux-gnu/qt4/bin/qmake
                              Qt 5.15.3 in PATH (qt5) /usr/lib/qt5/bin/qmake
                              Qt 5.15.3 in PATH (System) /usr/bin/qmake

                              1 Reply Last reply
                              0
                              • M Offline
                                M Offline
                                micha_eleric
                                wrote on last edited by
                                #22

                                i found another post that said to add

                                Q_DECLARE_METATYPE(QList<qfloat16>)
                                

                                but still gave same error while running.

                                1 Reply Last reply
                                0
                                • M micha_eleric

                                  @JKSH said in QObject::connect: Cannot queue arguments of type:

                                  @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                                  once i did find preference->kit->kit, nothing was listed under auto-detected nor manual

                                  That sounds very strange.

                                  What do you see when you try Step #2 in the instructions?

                                  lol, second step also gave no version, but can find editor version elsewhere
                                  Qt Creator 6.0.2
                                  Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                                  C Offline
                                  C Offline
                                  ChrisW67
                                  wrote on last edited by
                                  #23

                                  @micha_eleric If you are on Ubuntu 22.04 (a guess on my part), have not installed a Qt version separately from that installed by Ubuntu, and everything is up-to-date then you are using Qt 5.15.3.

                                  Open a terminal and type qmake -v

                                  M 1 Reply Last reply
                                  1
                                  • C ChrisW67

                                    @micha_eleric If you are on Ubuntu 22.04 (a guess on my part), have not installed a Qt version separately from that installed by Ubuntu, and everything is up-to-date then you are using Qt 5.15.3.

                                    Open a terminal and type qmake -v

                                    M Offline
                                    M Offline
                                    micha_eleric
                                    wrote on last edited by
                                    #24

                                    @ChrisW67 said in QObject::connect: Cannot queue arguments of type:

                                    @micha_eleric If you are on Ubuntu 22.04 (a guess on my part), have not installed a Qt version separately from that installed by Ubuntu, and everything is up-to-date then you are using Qt 5.15.3.

                                    Open a terminal and type qmake -v

                                    QMake version 3.1
                                    Using Qt version 5.15.3 in /usr/lib/x86_64-linux-gnu

                                    H 1 Reply Last reply
                                    0
                                    • M Offline
                                      M Offline
                                      micha_eleric
                                      wrote on last edited by
                                      #25

                                      in .h file, but only in one .h file

                                      Q_DECLARE_METATYPE(QList<qfloat16>)
                                      
                                      
                                      //data
                                      int id;
                                      

                                      in .cpp file, constructor

                                      id = qRegisterMetaType< QList<qfloat16> >();
                                      
                                      1 Reply Last reply
                                      0
                                      • M micha_eleric has marked this topic as solved on
                                      • M micha_eleric

                                        @Pl45m4 said in QObject::connect: Cannot queue arguments of type:

                                        @micha_eleric said in QObject::connect: Cannot queue arguments of type:

                                        Qt Creator 6.0.2
                                        Based on Qt 5.15.3 (GCC 11.2.0, 64 bit)

                                        This is meaningless. It's the Qt version which was used to build your QtCreator version.

                                        How are your build folders named? In some case they are named by default like:
                                        build_<Projectname>_<QtX_X_X>_<Compiler>_<Architecture>

                                        There you also can find out what Qt version you are using

                                        again nothing of use, "build-GraphicsView-Desktop-Debug"

                                        JKSHJ Offline
                                        JKSHJ Offline
                                        JKSH
                                        Moderators
                                        wrote on last edited by
                                        #26
                                        This post is deleted!
                                        1 Reply Last reply
                                        0
                                        • M micha_eleric

                                          @ChrisW67 said in QObject::connect: Cannot queue arguments of type:

                                          @micha_eleric If you are on Ubuntu 22.04 (a guess on my part), have not installed a Qt version separately from that installed by Ubuntu, and everything is up-to-date then you are using Qt 5.15.3.

                                          Open a terminal and type qmake -v

                                          QMake version 3.1
                                          Using Qt version 5.15.3 in /usr/lib/x86_64-linux-gnu

                                          H Offline
                                          H Offline
                                          HaoTian
                                          wrote on last edited by
                                          #27

                                          @micha_eleric Impossible! My demo runs fine and I'm using Qt version 5.6

                                          1 Reply Last reply
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