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QObject::connect returns false

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  • SPlattenS SPlatten

    @J-Hilk , @JonB , @KroMignon , I've looked at both moc files, moc_clsTimeEmu.cpp has the signal:

    // SIGNAL_0
    void clsTimeEmu::epoch(int _t1)
    {
        void *_a[] = { 0, const_cast<void*>reinterpret_cast<const void*>(&_t)) };
        QMetaObject::activate(this, &staticMetaObject, 0, _a);
    }
    

    moc_clsSchdSrv.cpp does not have anything that looks like the slot, no mention of updateTime at all, why ?

    JonBJ Online
    JonBJ Online
    JonB
    wrote on last edited by
    #29

    @SPlatten
    We have all said several times to try a complete delete and re-build.....

    1 Reply Last reply
    0
    • SPlattenS SPlatten

      @J-Hilk , clsSchdSrv.h, still a early work in progress:

      class clsSchdSrv : public QTimer {
          Q_OBJECT
      
      public:
          explicit clsSchdSrv(QObject* pParent = 0);
          void kick();
      
      public slots:
          virtual void expired() = 0;
      }
      

      Sorry, should have added:

      class clsTimeSync : public clsSchdSrv {
      public:
          explicit clsTimeSync();
      
      public slots:
          virtual void expired();
          void updateTime(int intTimeNow);
      }
      
      jsulmJ Offline
      jsulmJ Offline
      jsulm
      Lifetime Qt Champion
      wrote on last edited by
      #30

      @SPlatten You should see a warning at runtime when connect is executed: what does it say?

      https://forum.qt.io/topic/113070/qt-code-of-conduct

      1 Reply Last reply
      0
      • KroMignonK KroMignon

        @SPlatten said in QObject::connect returns false:

        moc_clsSchdSrv.cpp does not have anything that looks like the slot, no mention of updateTime at all, why ?

        Some time Qt-Creator do not detect changes is HEADERS files, so moc will not be re-run.
        This is why I suggest you to try to re-run yourself qmake and, if this not help, remove the build directory (as also suggested by @JonB ) to force full rebuild (with moc).

        But first, make sure all headers are present in HEADERS of your PRO file.

        SPlattenS Offline
        SPlattenS Offline
        SPlatten
        wrote on last edited by
        #31

        @KroMignon, I deleted the content of the build folder , checking for any hidden files, then ran clean, remake and build, same results.

        Kind Regards,
        Sy

        1 Reply Last reply
        0
        • SPlattenS SPlatten

          @J-Hilk , clsSchdSrv.h, still a early work in progress:

          class clsSchdSrv : public QTimer {
              Q_OBJECT
          
          public:
              explicit clsSchdSrv(QObject* pParent = 0);
              void kick();
          
          public slots:
              virtual void expired() = 0;
          }
          

          Sorry, should have added:

          class clsTimeSync : public clsSchdSrv {
          public:
              explicit clsTimeSync();
          
          public slots:
              virtual void expired();
              void updateTime(int intTimeNow);
          }
          
          J.HilkJ Online
          J.HilkJ Online
          J.Hilk
          Moderators
          wrote on last edited by
          #32

          @SPlatten if thats the header, than I as well fail to see the slot void updateTime(long); declaration ;)


          Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


          Q: What's that?
          A: It's blue light.
          Q: What does it do?
          A: It turns blue.

          1 Reply Last reply
          0
          • SPlattenS SPlatten

            @J-Hilk , clsSchdSrv.h, still a early work in progress:

            class clsSchdSrv : public QTimer {
                Q_OBJECT
            
            public:
                explicit clsSchdSrv(QObject* pParent = 0);
                void kick();
            
            public slots:
                virtual void expired() = 0;
            }
            

            Sorry, should have added:

            class clsTimeSync : public clsSchdSrv {
            public:
                explicit clsTimeSync();
            
            public slots:
                virtual void expired();
                void updateTime(int intTimeNow);
            }
            
            JonBJ Online
            JonBJ Online
            JonB
            wrote on last edited by JonB
            #33

            @SPlatten said in QObject::connect returns false:

            public slots:
            virtual void expired() = 0;

            But you use SLOT(updateTime())?

            Why are you showing us clsSchdSrv? Earlier you showed clsTimeSync?

            SPlattenS 1 Reply Last reply
            0
            • SPlattenS SPlatten

              @J-Hilk , clsSchdSrv.h, still a early work in progress:

              class clsSchdSrv : public QTimer {
                  Q_OBJECT
              
              public:
                  explicit clsSchdSrv(QObject* pParent = 0);
                  void kick();
              
              public slots:
                  virtual void expired() = 0;
              }
              

              Sorry, should have added:

              class clsTimeSync : public clsSchdSrv {
              public:
                  explicit clsTimeSync();
              
              public slots:
                  virtual void expired();
                  void updateTime(int intTimeNow);
              }
              
              KroMignonK Offline
              KroMignonK Offline
              KroMignon
              wrote on last edited by
              #34

              @SPlatten said in QObject::connect returns false:

              clsSchdSrv.h, still a early work in progress:

              I am not sure, you can declare a slot as virtual.
              I would change this to:

              class clsSchdSrv : public QTimer {
                  Q_OBJECT
              
              public:
                  explicit clsSchdSrv(QObject* pParent = 0);
                  void kick();
              
              public:
                   virtual void  onExpired() = 0;
              public slots:
                  void expired() {  onExpired(); } 
              }
              

              It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

              1 Reply Last reply
              0
              • JonBJ JonB

                @SPlatten said in QObject::connect returns false:

                public slots:
                virtual void expired() = 0;

                But you use SLOT(updateTime())?

                Why are you showing us clsSchdSrv? Earlier you showed clsTimeSync?

                SPlattenS Offline
                SPlattenS Offline
                SPlatten
                wrote on last edited by
                #35

                @JonB , please see the edited post which includes the derived class, sorry.

                Kind Regards,
                Sy

                J.HilkJ KroMignonK JonBJ 3 Replies Last reply
                0
                • SPlattenS SPlatten

                  @JonB , please see the edited post which includes the derived class, sorry.

                  J.HilkJ Online
                  J.HilkJ Online
                  J.Hilk
                  Moderators
                  wrote on last edited by J.Hilk
                  #36

                  @SPlatten your derived class will need the Q_OBJECT macro as well, if it defines slots/signals


                  Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                  Q: What's that?
                  A: It's blue light.
                  Q: What does it do?
                  A: It turns blue.

                  SPlattenS 1 Reply Last reply
                  1
                  • SPlattenS SPlatten

                    @JonB , please see the edited post which includes the derived class, sorry.

                    KroMignonK Offline
                    KroMignonK Offline
                    KroMignon
                    wrote on last edited by
                    #37

                    @SPlatten said in QObject::connect returns false:

                    please see the edited post which includes the derived class, sorry.

                    In this header signal signature is void updateTime(int) and not void updateTime(long)

                    It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                    JonBJ SPlattenS 2 Replies Last reply
                    0
                    • SPlattenS SPlatten

                      @JonB , please see the edited post which includes the derived class, sorry.

                      JonBJ Online
                      JonBJ Online
                      JonB
                      wrote on last edited by
                      #38

                      @SPlatten
                      class clsTimeSync : public clsSchdSrv {
                      Although updateTime() is only a slot and not a signal, you do not have Q_OBJECT in this class. Does it help if you do (and then rebuild from scratch)?

                      1 Reply Last reply
                      0
                      • KroMignonK KroMignon

                        @SPlatten said in QObject::connect returns false:

                        please see the edited post which includes the derived class, sorry.

                        In this header signal signature is void updateTime(int) and not void updateTime(long)

                        JonBJ Online
                        JonBJ Online
                        JonB
                        wrote on last edited by
                        #39

                        @KroMignon said in QObject::connect returns false:

                        In this header signal signature is void updateTime(int) and not void updateTime(long)

                        That's coz he has changed per earlier on.
                        I agree we do not know for sure what his code is, but I think he dealt with that alteration.

                        1 Reply Last reply
                        0
                        • J.HilkJ J.Hilk

                          @SPlatten your derived class will need the Q_OBJECT macro as well, if it defines slots/signals

                          SPlattenS Offline
                          SPlattenS Offline
                          SPlatten
                          wrote on last edited by
                          #40

                          @J-Hilk , why? The class it inherits already has that.

                          Kind Regards,
                          Sy

                          JonBJ KroMignonK 3 Replies Last reply
                          0
                          • KroMignonK KroMignon

                            @SPlatten said in QObject::connect returns false:

                            please see the edited post which includes the derived class, sorry.

                            In this header signal signature is void updateTime(int) and not void updateTime(long)

                            SPlattenS Offline
                            SPlattenS Offline
                            SPlatten
                            wrote on last edited by
                            #41

                            @KroMignon , because I changed it from long to int after earlier posts.

                            Kind Regards,
                            Sy

                            1 Reply Last reply
                            0
                            • SPlattenS SPlatten

                              @J-Hilk , why? The class it inherits already has that.

                              JonBJ Online
                              JonBJ Online
                              JonB
                              wrote on last edited by JonB
                              #42

                              @SPlatten said in QObject::connect returns false:

                              @J-Hilk , why? The class it inherits already has that.

                              That's not how it works. Which is why I said to try putting Q_OBJECT in.

                              Can you please do that and then we will discuss why if it makes any difference?

                              SPlattenS 1 Reply Last reply
                              0
                              • JonBJ JonB

                                @SPlatten said in QObject::connect returns false:

                                @J-Hilk , why? The class it inherits already has that.

                                That's not how it works. Which is why I said to try putting Q_OBJECT in.

                                Can you please do that and then we will discuss why if it makes any difference?

                                SPlattenS Offline
                                SPlattenS Offline
                                SPlatten
                                wrote on last edited by
                                #43

                                @JonB , adding Q_OBJECT to the inherit class results in the compiler error:

                                undefined erference to `vtable for clsTimeSync`
                                

                                Kind Regards,
                                Sy

                                jsulmJ SPlattenS 2 Replies Last reply
                                0
                                • SPlattenS SPlatten

                                  @JonB , adding Q_OBJECT to the inherit class results in the compiler error:

                                  undefined erference to `vtable for clsTimeSync`
                                  
                                  jsulmJ Offline
                                  jsulmJ Offline
                                  jsulm
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #44

                                  @SPlatten said in QObject::connect returns false:

                                  results in the compiler error

                                  You need to do a complete rebuild

                                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  JonBJ 1 Reply Last reply
                                  0
                                  • SPlattenS SPlatten

                                    @J-Hilk , why? The class it inherits already has that.

                                    KroMignonK Offline
                                    KroMignonK Offline
                                    KroMignon
                                    wrote on last edited by
                                    #45

                                    @SPlatten said in QObject::connect returns false:

                                    why? The class it inherits already has that.

                                    Because it is a Qt recommendation (cf. https://doc.qt.io/qt-5/metaobjects.html)

                                    The meta-object system is based on three things:

                                    • The QObject class provides a base class for objects that can take advantage of the meta-object system.
                                    • The Q_OBJECT macro inside the private section of the class declaration is used to enable meta-object features, such as dynamic properties, signals, and slots.
                                    • The Meta-Object Compiler (moc) supplies each QObject subclass with the necessary code to implement meta-object features.

                                    It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                                    1 Reply Last reply
                                    1
                                    • SPlattenS SPlatten

                                      @JonB , adding Q_OBJECT to the inherit class results in the compiler error:

                                      undefined erference to `vtable for clsTimeSync`
                                      
                                      SPlattenS Offline
                                      SPlattenS Offline
                                      SPlatten
                                      wrote on last edited by
                                      #46

                                      @KroMignon , @JonB , @J-Hilk , @jsulm , ok, works now I think the missing Q_OBJECT was the issue as having cleaned out the build folder, remake, rebuild, now it works.

                                      Kind Regards,
                                      Sy

                                      1 Reply Last reply
                                      1
                                      • jsulmJ jsulm

                                        @SPlatten said in QObject::connect returns false:

                                        results in the compiler error

                                        You need to do a complete rebuild

                                        JonBJ Online
                                        JonBJ Online
                                        JonB
                                        wrote on last edited by
                                        #47

                                        @jsulm said in QObject::connect returns false:

                                        You need to do a complete rebuild

                                        As we have said over & over again, it would be nice if people followed that instead of ignoring it.....

                                        1 Reply Last reply
                                        1
                                        • SPlattenS SPlatten

                                          @J-Hilk , why? The class it inherits already has that.

                                          JonBJ Online
                                          JonBJ Online
                                          JonB
                                          wrote on last edited by JonB
                                          #48

                                          @SPlatten said in QObject::connect returns false:

                                          @J-Hilk , why? The class it inherits already has that.

                                          Q_OBJECT is a macro. You can look at what it does.

                                          I know the rule is:

                                          • Every class which defines signals MUST have Q_OBJECT in that class definition. Inheritance from parent is not what it's about.

                                          • Normally I believe slot-only classes do not have to have Q_OBJECT. HOWEVER I only work with the new-style connect() syntax, not available in Qt4. It may be that to use SLOT() you do also need Q_OBJECT in old style? When in doubt --- and certainly if I were having a problem --- I would put Q_OBJECT into classes with slots just in case.....

                                          1 Reply Last reply
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