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pointer paramters c++

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  • H hye2
    mainwindow.cpp
    
    mainwindow::mainwindow(Qwidget *parent) : QmainWindow(parent), ui(new Ui::MainWindow)
    {
    ui ->setupUi(this);
    QpushButton *button = new Qpushbutton("button");
    connect(button, SIGNAL(clicked(CurrentState*,char)), this,   SLOT(on_button_clicked(CurrentState*,char)));
    }
    
    MainWindow::~MainWindow()
    {
    delete ui;
    }
    
    void MainWindow::on_button_clicked(CurrentState *state,char number)
    {
    ui->button->setText(state->value);
    }
    
    mainwindow.h
    
    ~~
    public slots:
    void on_button_clicked(CurrentState *state,char number);
    

    Here is my code,,

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by
    #11

    @hye2 said in pointer paramters c++:

    QpushButton

    QPushButton has no such signal!
    Please read documentation: https://doc.qt.io/qt-5/qabstractbutton.html#clicked

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

    H 1 Reply Last reply
    2
    • jsulmJ jsulm

      @hye2 said in pointer paramters c++:

      QpushButton

      QPushButton has no such signal!
      Please read documentation: https://doc.qt.io/qt-5/qabstractbutton.html#clicked

      H Offline
      H Offline
      hye2
      wrote on last edited by hye2
      #12

      @jsulm said in pointer paramters c++:

      QPushButton has no such signal!

      oh.. you mean..
      I have to use void QAbstractButton::clicked(bool checked = false) this..? sorry

      jsulmJ 1 Reply Last reply
      0
      • H hye2

        @jsulm said in pointer paramters c++:

        QPushButton has no such signal!

        oh.. you mean..
        I have to use void QAbstractButton::clicked(bool checked = false) this..? sorry

        jsulmJ Offline
        jsulmJ Offline
        jsulm
        Lifetime Qt Champion
        wrote on last edited by
        #13

        @hye2 You can only use signals which exist. If you want to pass additional parameters to your slot switch to Qt5 connect syntax and use a lambda as slot.

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

        H 1 Reply Last reply
        0
        • jsulmJ jsulm

          @hye2 You can only use signals which exist. If you want to pass additional parameters to your slot switch to Qt5 connect syntax and use a lambda as slot.

          H Offline
          H Offline
          hye2
          wrote on last edited by
          #14

          @jsulm

          I see. Can you help me a little?... I've never used Lambda before...

          JonBJ 1 Reply Last reply
          0
          • H hye2

            @jsulm

            I see. Can you help me a little?... I've never used Lambda before...

            JonBJ Offline
            JonBJ Offline
            JonB
            wrote on last edited by JonB
            #15

            @hye2
            Search https://wiki.qt.io/New_Signal_Slot_Syntax and https://doc.qt.io/qt-5/signalsandslots.html for lambda to see a couple of examples. Otherwise lambdas are a feature of C++ nothing to do with Qt, you can look them up in a C++ reference/tutorial. And while you are here stop using your old style SIGNAL/SLOT() macros and switch over the new style connect()s.

            H 2 Replies Last reply
            3
            • JonBJ JonB

              @hye2
              Search https://wiki.qt.io/New_Signal_Slot_Syntax and https://doc.qt.io/qt-5/signalsandslots.html for lambda to see a couple of examples. Otherwise lambdas are a feature of C++ nothing to do with Qt, you can look them up in a C++ reference/tutorial. And while you are here stop using your old style SIGNAL/SLOT() macros and switch over the new style connect()s.

              H Offline
              H Offline
              hye2
              wrote on last edited by
              #16

              @JonB

              Thank you! :)

              1 Reply Last reply
              0
              • JonBJ JonB

                @hye2
                Search https://wiki.qt.io/New_Signal_Slot_Syntax and https://doc.qt.io/qt-5/signalsandslots.html for lambda to see a couple of examples. Otherwise lambdas are a feature of C++ nothing to do with Qt, you can look them up in a C++ reference/tutorial. And while you are here stop using your old style SIGNAL/SLOT() macros and switch over the new style connect()s.

                H Offline
                H Offline
                hye2
                wrote on last edited by
                #17

                @JonB

                [](CurrentState *state, char number){ //something }

                it is right..?

                JonBJ S 2 Replies Last reply
                0
                • H hye2

                  @JonB

                  [](CurrentState *state, char number){ //something }

                  it is right..?

                  JonBJ Offline
                  JonBJ Offline
                  JonB
                  wrote on last edited by JonB
                  #18

                  @hye2 said in pointer paramters c++:

                  [](CurrentState *state, char number){ //something }

                  Yes, that is the right syntax:

                  • Inside the [...] you pass any context/local variables from where you are defining the lambda that you want the lambda to have access to, if any.
                  • Inside the (...) you declare the parameters which the signal passes to the slot, if any.

                  For example, a slot for QLineEdit::textChanged(const QString &text) signal applied to a whole bunch of QLineEdits where we want to know which one was changed, as well as the new text:

                  for (QLineEdit *lineEdit : bunchOfLineEdits)
                      connect(lineEdit, &QLineEdit::textChanged, [lineEdit](const QString &text) { qDebug() << lineEdit->objectName() << text; });
                  
                  H 1 Reply Last reply
                  1
                  • JonBJ JonB

                    @hye2 said in pointer paramters c++:

                    [](CurrentState *state, char number){ //something }

                    Yes, that is the right syntax:

                    • Inside the [...] you pass any context/local variables from where you are defining the lambda that you want the lambda to have access to, if any.
                    • Inside the (...) you declare the parameters which the signal passes to the slot, if any.

                    For example, a slot for QLineEdit::textChanged(const QString &text) signal applied to a whole bunch of QLineEdits where we want to know which one was changed, as well as the new text:

                    for (QLineEdit *lineEdit : bunchOfLineEdits)
                        connect(lineEdit, &QLineEdit::textChanged, [lineEdit](const QString &text) { qDebug() << lineEdit->objectName() << text; });
                    
                    H Offline
                    H Offline
                    hye2
                    wrote on last edited by
                    #19

                    @JonB

                    Ok like this..?

                    mainwindow.cpp

                    QpushButton *button = new Qpushbutton("button");
                    connect(button, Qpushbutton::clicked,[button](CurrentState *state, char number){ //somthing } );
                    
                    JonBJ 1 Reply Last reply
                    0
                    • H hye2

                      @JonB

                      [](CurrentState *state, char number){ //something }

                      it is right..?

                      S Offline
                      S Offline
                      SimonSchroeder
                      wrote on last edited by
                      #20

                      @hye2 said in pointer paramters c++:

                      [](CurrentState *state, char number){ //something }
                      it is right..?

                      Well, the syntax is right for a lambda. However, in the context of what you are trying to achieve it will not help. QPushButton has a signal clicked(bool). So, your 'slot' (which will be the lambda in this case) has to have a bool as parameter or no parameter at all (you can drop parameters from the end of the function call when using slots).

                      I assume that state and number are member variables of your class. In this case you need to capture this inside the lambda to have access to these. The lambda you are most likely looking for is [this](){ on_button_clicked(state, number); }.

                      1 Reply Last reply
                      1
                      • J.HilkJ Offline
                        J.HilkJ Offline
                        J.Hilk
                        Moderators
                        wrote on last edited by
                        #21

                        I'm getting the feeling, you're trying to run before you can crawl.

                        why don't you simply subclass QPushButton, add the signal you want and emit it where and when you want it, with the parameters you specified.


                        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
                        1
                        • H hye2

                          @JonB

                          Ok like this..?

                          mainwindow.cpp

                          QpushButton *button = new Qpushbutton("button");
                          connect(button, Qpushbutton::clicked,[button](CurrentState *state, char number){ //somthing } );
                          
                          JonBJ Offline
                          JonBJ Offline
                          JonB
                          wrote on last edited by JonB
                          #22

                          @hye2

                          connect(button, Qpushbutton::clicked,[button](CurrentState *state, char number){ //somthing } );

                          • You only need to pass [button] if you will wish to access button in your { ... } lambda body code, else it's not needed.

                          • QPushbutton::clicked, [...](CurrentState *state, char number) cannot be right because the signature for the signal is void QAbstractButton::clicked(bool checked = false), and you cannot alter that fact. You can add further parameters to the slot in the lambda's [...], but you cannot alter what is inside the (...) unless you define your own signal which passes extra/different parameters. So where exactly do your CurrentState *state, char number come from?

                          1 Reply Last reply
                          2
                          • H Offline
                            H Offline
                            hye2
                            wrote on last edited by hye2
                            #23
                            This post is deleted!
                            JonBJ 1 Reply Last reply
                            0
                            • H hye2

                              This post is deleted!

                              JonBJ Offline
                              JonBJ Offline
                              JonB
                              wrote on last edited by
                              #24

                              @hye2 said in pointer paramters c++:

                              It come from other cpp(inside project) for connect to device

                              That does not mean much to me. What does it have to do with the QPushButton::clicked signal? Why/how does it get passed from a signal to your slot? Can your connect() statement "see" these variables? Or are these variables just as "visible" to your slot code? You need to understand this in order for you or anybody else to answer what you will need, saying "My boss wants to create a Gui using the existing code.." won't help....

                              H 1 Reply Last reply
                              0
                              • JonBJ JonB

                                @hye2 said in pointer paramters c++:

                                It come from other cpp(inside project) for connect to device

                                That does not mean much to me. What does it have to do with the QPushButton::clicked signal? Why/how does it get passed from a signal to your slot? Can your connect() statement "see" these variables? Or are these variables just as "visible" to your slot code? You need to understand this in order for you or anybody else to answer what you will need, saying "My boss wants to create a Gui using the existing code.." won't help....

                                H Offline
                                H Offline
                                hye2
                                wrote on last edited by hye2
                                #25

                                Oh, you asked me that. I got it wrong.

                                State is to get a value from the machine's current state, so when you click on a button, it sends a value to another function and prints the changed state value back on the label, and the number is to get the current machine's number.

                                So I tried to use state, number

                                Here is my sample code

                                void MainWindow::on_button_clicked(Secret *secret, CurrentState *state, char number)
                                {
                                double value;
                                Qstring value1;
                                value1 = ui ->valueLine -> text();
                                value = value1.toDouble();
                                
                                char i;
                                quency(&secret[0], value);
                                for(i = 0; i <number; i++){
                                }
                                     ui -> Name -> setText(state->quency_value);
                                }
                                

                                Before I tried to get the value elsewhere, but I gave up because I couldn't use state

                                JonBJ 1 Reply Last reply
                                0
                                • H hye2

                                  Oh, you asked me that. I got it wrong.

                                  State is to get a value from the machine's current state, so when you click on a button, it sends a value to another function and prints the changed state value back on the label, and the number is to get the current machine's number.

                                  So I tried to use state, number

                                  Here is my sample code

                                  void MainWindow::on_button_clicked(Secret *secret, CurrentState *state, char number)
                                  {
                                  double value;
                                  Qstring value1;
                                  value1 = ui ->valueLine -> text();
                                  value = value1.toDouble();
                                  
                                  char i;
                                  quency(&secret[0], value);
                                  for(i = 0; i <number; i++){
                                  }
                                       ui -> Name -> setText(state->quency_value);
                                  }
                                  

                                  Before I tried to get the value elsewhere, but I gave up because I couldn't use state

                                  JonBJ Offline
                                  JonBJ Offline
                                  JonB
                                  wrote on last edited by JonB
                                  #26

                                  @hye2

                                  State is to get a value from the machine's current state

                                  I'm afraid this isn't clear enough to give you an answer. What does this have to do with the button, or clicking it? Do you have multiple buttons each of which each are (somehow) associated with a different machine/state? Or do you only have one machine state regardless of button? Or what?

                                  [This post made before you showed code, looking at that now...]

                                  Your code does not help answer the question. It shows your "desired" slot behaviour, but that is not what matters. You are not explaining where the parameters you show this slot taking come from, whether they vary per button etc. I cannot keep asking for clarification on that, so I cannot tell you how to write the signal/slot/lambda till that is clear....

                                  H 1 Reply Last reply
                                  0
                                  • JonBJ JonB

                                    @hye2

                                    State is to get a value from the machine's current state

                                    I'm afraid this isn't clear enough to give you an answer. What does this have to do with the button, or clicking it? Do you have multiple buttons each of which each are (somehow) associated with a different machine/state? Or do you only have one machine state regardless of button? Or what?

                                    [This post made before you showed code, looking at that now...]

                                    Your code does not help answer the question. It shows your "desired" slot behaviour, but that is not what matters. You are not explaining where the parameters you show this slot taking come from, whether they vary per button etc. I cannot keep asking for clarification on that, so I cannot tell you how to write the signal/slot/lambda till that is clear....

                                    H Offline
                                    H Offline
                                    hye2
                                    wrote on last edited by
                                    #27

                                    @JonB

                                    Do you have multiple buttons each of which each are (somehow) associated with a different machine/state? yes
                                    Or do you only have one machine state regardless of button? yes it have one maichine state regardless of button

                                    machine state just one, but it has muliple button

                                    JonBJ 1 Reply Last reply
                                    0
                                    • H hye2

                                      @JonB

                                      Do you have multiple buttons each of which each are (somehow) associated with a different machine/state? yes
                                      Or do you only have one machine state regardless of button? yes it have one maichine state regardless of button

                                      machine state just one, but it has muliple button

                                      JonBJ Offline
                                      JonBJ Offline
                                      JonB
                                      wrote on last edited by JonB
                                      #28

                                      @hye2 said in pointer paramters c++:

                                      Do you have multiple buttons each of which each are (somehow) associated with a different machine/state? yes
                                      Or do you only have one machine state regardless of button? yes it have one maichine state regardless of button

                                      You are not helping yourself or me with your answers. You need to think about them! This is not possible. I asked you whether you have one single machine state OR separate machine states per button. And you have answered "yes" to both! :( "Yes" you have different machines/states and "Yes" you only have one machine/state....

                                      machine state just one, but it has muliple button

                                      If there is only one machine/state, why do you need to pass it as a parameter in any clicked signal, you can just as easily retrieve it directly from the slot, it does not need to be a parameter from the signal?

                                      Please think about what the situation is/what you need to achieve if you want proper help.

                                      For the last time: what different parameters do you actually need to pass from a button's clicked signal to a slot? What varies per button? (secret? state? number?)

                                      H 1 Reply Last reply
                                      2
                                      • JonBJ JonB

                                        @hye2 said in pointer paramters c++:

                                        Do you have multiple buttons each of which each are (somehow) associated with a different machine/state? yes
                                        Or do you only have one machine state regardless of button? yes it have one maichine state regardless of button

                                        You are not helping yourself or me with your answers. You need to think about them! This is not possible. I asked you whether you have one single machine state OR separate machine states per button. And you have answered "yes" to both! :( "Yes" you have different machines/states and "Yes" you only have one machine/state....

                                        machine state just one, but it has muliple button

                                        If there is only one machine/state, why do you need to pass it as a parameter in any clicked signal, you can just as easily retrieve it directly from the slot, it does not need to be a parameter from the signal?

                                        Please think about what the situation is/what you need to achieve if you want proper help.

                                        For the last time: what different parameters do you actually need to pass from a button's clicked signal to a slot? What varies per button? (secret? state? number?)

                                        H Offline
                                        H Offline
                                        hye2
                                        wrote on last edited by hye2
                                        #29

                                        @JonB

                                        I'm sorry for the late reply.
                                        One state means one machine state, and there are various states in it.
                                        For example, there are various values such as the number, current value, and somevalue.
                                        Each button receives a corresponding value, sends it to the corresponding function (like a quency), and reads the value to the state

                                        The parameters were needed to transmit state and secret values to the quency(or other value).
                                        I tried to use state and secret by sending the input value to another place, but it failed, so I was just thinking about calling the parameters.

                                        what different parameters do you actually need to pass from a button's clicked signal to a slot? :
                                        I use parameters just for send value and print state

                                        quency(&secret[0], value);
                                        
                                        ui -> Name -> setText(state->quency_value)
                                        

                                        What varies per button? (secret? state? number?) : all same i just use that parameter for send value and print state

                                        JonBJ 1 Reply Last reply
                                        0
                                        • H hye2

                                          @JonB

                                          I'm sorry for the late reply.
                                          One state means one machine state, and there are various states in it.
                                          For example, there are various values such as the number, current value, and somevalue.
                                          Each button receives a corresponding value, sends it to the corresponding function (like a quency), and reads the value to the state

                                          The parameters were needed to transmit state and secret values to the quency(or other value).
                                          I tried to use state and secret by sending the input value to another place, but it failed, so I was just thinking about calling the parameters.

                                          what different parameters do you actually need to pass from a button's clicked signal to a slot? :
                                          I use parameters just for send value and print state

                                          quency(&secret[0], value);
                                          
                                          ui -> Name -> setText(state->quency_value)
                                          

                                          What varies per button? (secret? state? number?) : all same i just use that parameter for send value and print state

                                          JonBJ Offline
                                          JonBJ Offline
                                          JonB
                                          wrote on last edited by JonB
                                          #30

                                          @hye2
                                          I am sorry but I don't understand the explanation you give. Maybe someone else does, but I do not.

                                          I have tried to ask why you need to pass the various things you do as arguments to the signal to be passed to the slot as opposed to just fetching them directly from the slot code without reference to the signal, but cannot find an answer in what you have written. Only you know the answer to this, but I cannot seem to extract anything clear and simple from you. So cannot tell you what you need.

                                          All I will say, in case it helps, is: while you cannot alter what parameters existing signals pass, you can define your own signals with whatever parameters you wish. You can also emit your own signals, with whatever parameters you wish, in the slot/lambda code you attach to an existing signal. And you can "chain" new signal emission onto existing signals's slots. So for example you have code like:

                                          signals:
                                              buttonClickedWithExtendedParameters(QPushButton *button, CurrentState *state, char number)
                                          
                                          connect(button, &QPushButton::clicked, [button, this]() { emit buttonClickedWithExtendedParameters(button, this->state, this->number); });
                                          
                                          void Class::onButtonClickedWithExtendedParameters(QPushButton *button, CurrentState *state, char number)
                                          {
                                          }
                                          

                                          Where you would get the state & number from --- which are needed in the connect() statement and whose values will be evaluated at runtime when the signal is raised --- I have not understood from what you have written.

                                          1 Reply Last reply
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