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Change only a specific Default Parameter on a function



2019 Community Moderator ElectionUse of 'const' for function parametersUse 'class' or 'typename' for template parameters?Why can templates only be implemented in the header file?Why do we need virtual functions in C++?Where to put default parameter value in C++?Why does changing 0.1f to 0 slow down performance by 10x?QInputDialog Parameter DefaultsAre the days of passing const std::string & as a parameter over?Qt: How to call a set to a toString, return in get function and testing a boolCan`t overload the operator << for a my own class












9















I'm using qt and I am trying to use the QInputDialog::getText() function to get input from the user, from the Documentation the definition of the function is:



QString QInputDialog::getText(QWidget * parent, const QString & title, const QString & label, QLineEdit::EchoMode mode = QLineEdit::Normal, const QString & text = QString(), bool * ok = 0, Qt::WindowFlags flags = 0, Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


and here is my code:



bool ok=0;
newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
"Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
,&ok);


but I get the Error:



error: no matching function for call to 'QInputDialog::getText(int, const char [29], const char [80], bool*)'
,&ok);
^


but when I pass in all the arguments before the *ok argument like:



bool ok=0;
newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
"Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
,QLineEdit::Normal,
QString(),&ok);


it works.



I really don't understand why cant I just change the default parameter I want and leave the rest as default?.










share|improve this question





























    9















    I'm using qt and I am trying to use the QInputDialog::getText() function to get input from the user, from the Documentation the definition of the function is:



    QString QInputDialog::getText(QWidget * parent, const QString & title, const QString & label, QLineEdit::EchoMode mode = QLineEdit::Normal, const QString & text = QString(), bool * ok = 0, Qt::WindowFlags flags = 0, Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


    and here is my code:



    bool ok=0;
    newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
    "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
    ,&ok);


    but I get the Error:



    error: no matching function for call to 'QInputDialog::getText(int, const char [29], const char [80], bool*)'
    ,&ok);
    ^


    but when I pass in all the arguments before the *ok argument like:



    bool ok=0;
    newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
    "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
    ,QLineEdit::Normal,
    QString(),&ok);


    it works.



    I really don't understand why cant I just change the default parameter I want and leave the rest as default?.










    share|improve this question



























      9












      9








      9








      I'm using qt and I am trying to use the QInputDialog::getText() function to get input from the user, from the Documentation the definition of the function is:



      QString QInputDialog::getText(QWidget * parent, const QString & title, const QString & label, QLineEdit::EchoMode mode = QLineEdit::Normal, const QString & text = QString(), bool * ok = 0, Qt::WindowFlags flags = 0, Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


      and here is my code:



      bool ok=0;
      newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
      "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
      ,&ok);


      but I get the Error:



      error: no matching function for call to 'QInputDialog::getText(int, const char [29], const char [80], bool*)'
      ,&ok);
      ^


      but when I pass in all the arguments before the *ok argument like:



      bool ok=0;
      newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
      "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
      ,QLineEdit::Normal,
      QString(),&ok);


      it works.



      I really don't understand why cant I just change the default parameter I want and leave the rest as default?.










      share|improve this question
















      I'm using qt and I am trying to use the QInputDialog::getText() function to get input from the user, from the Documentation the definition of the function is:



      QString QInputDialog::getText(QWidget * parent, const QString & title, const QString & label, QLineEdit::EchoMode mode = QLineEdit::Normal, const QString & text = QString(), bool * ok = 0, Qt::WindowFlags flags = 0, Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


      and here is my code:



      bool ok=0;
      newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
      "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
      ,&ok);


      but I get the Error:



      error: no matching function for call to 'QInputDialog::getText(int, const char [29], const char [80], bool*)'
      ,&ok);
      ^


      but when I pass in all the arguments before the *ok argument like:



      bool ok=0;
      newAddress = QInputDialog::getText(0,"Enter an Address to Validate",
      "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)"
      ,QLineEdit::Normal,
      QString(),&ok);


      it works.



      I really don't understand why cant I just change the default parameter I want and leave the rest as default?.







      c++ qt qt5






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 19 hours ago







      Makhele Sabata

















      asked yesterday









      Makhele SabataMakhele Sabata

      8916




      8916
























          3 Answers
          3






          active

          oldest

          votes


















          12














          When you pass a value for a particular parameter that has a default argument, you have to pass values for all the default parameters before it. Otherwise, the value you have passed will be taken as the value for the first default parameter.



          So you have to do this:



          newAddress = QInputDialog::getText(
          0,
          "Enter an Address to Validate",
          "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
          QLineEdit::Normal,
          QString(),
          &ok);


          You can leave out passing values for the parameters after bool * parameter.



          The C++ standard states in [dcl.fct.default]/1




          Default arguments will be used in calls where trailing arguments are missing.







          share|improve this answer


























          • I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

            – Makhele Sabata
            21 hours ago













          • You are welcome.

            – P.W
            21 hours ago



















          7














          In C++ you can only use (one or multiple) default parameters at the end of the parameter list. If you omit parameters in the middle, the compiler has no way of knowing, which argument belongs to which parameter. Therefore you have to specify the default parameters QLineEdit::Normal and QString() manually before passing &ok.



          In your not working case the compiler tries to match your bool pointer to the next type in the parameter list, which is QLineEdit::EchoMode and therefore not compatible.






          share|improve this answer































            1














            the error is beacuse of the optional paramteres:



            QString QInputDialog::getText(
            QWidget * parent,
            const QString & title,
            const QString & label,
            QLineEdit::EchoMode mode = QLineEdit::Normal,
            const QString& text = QString(),
            bool * ok = 0,
            Qt::WindowFlags flags = 0,
            Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


            QInputDialog::getText(
            0,
            "Enter an Address to Validate",
            "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
            --> QLineEdit::EchoMode ??
            --> QString& text ??
            &ok);


            if you set one optional parameter, you have to set all the optional paramteters to the left of that, in your case QLineEdit::EchoMode and QString& text






            share|improve this answer























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              3 Answers
              3






              active

              oldest

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              3 Answers
              3






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              12














              When you pass a value for a particular parameter that has a default argument, you have to pass values for all the default parameters before it. Otherwise, the value you have passed will be taken as the value for the first default parameter.



              So you have to do this:



              newAddress = QInputDialog::getText(
              0,
              "Enter an Address to Validate",
              "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
              QLineEdit::Normal,
              QString(),
              &ok);


              You can leave out passing values for the parameters after bool * parameter.



              The C++ standard states in [dcl.fct.default]/1




              Default arguments will be used in calls where trailing arguments are missing.







              share|improve this answer


























              • I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

                – Makhele Sabata
                21 hours ago













              • You are welcome.

                – P.W
                21 hours ago
















              12














              When you pass a value for a particular parameter that has a default argument, you have to pass values for all the default parameters before it. Otherwise, the value you have passed will be taken as the value for the first default parameter.



              So you have to do this:



              newAddress = QInputDialog::getText(
              0,
              "Enter an Address to Validate",
              "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
              QLineEdit::Normal,
              QString(),
              &ok);


              You can leave out passing values for the parameters after bool * parameter.



              The C++ standard states in [dcl.fct.default]/1




              Default arguments will be used in calls where trailing arguments are missing.







              share|improve this answer


























              • I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

                – Makhele Sabata
                21 hours ago













              • You are welcome.

                – P.W
                21 hours ago














              12












              12








              12







              When you pass a value for a particular parameter that has a default argument, you have to pass values for all the default parameters before it. Otherwise, the value you have passed will be taken as the value for the first default parameter.



              So you have to do this:



              newAddress = QInputDialog::getText(
              0,
              "Enter an Address to Validate",
              "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
              QLineEdit::Normal,
              QString(),
              &ok);


              You can leave out passing values for the parameters after bool * parameter.



              The C++ standard states in [dcl.fct.default]/1




              Default arguments will be used in calls where trailing arguments are missing.







              share|improve this answer















              When you pass a value for a particular parameter that has a default argument, you have to pass values for all the default parameters before it. Otherwise, the value you have passed will be taken as the value for the first default parameter.



              So you have to do this:



              newAddress = QInputDialog::getText(
              0,
              "Enter an Address to Validate",
              "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
              QLineEdit::Normal,
              QString(),
              &ok);


              You can leave out passing values for the parameters after bool * parameter.



              The C++ standard states in [dcl.fct.default]/1




              Default arguments will be used in calls where trailing arguments are missing.








              share|improve this answer














              share|improve this answer



              share|improve this answer








              edited 23 hours ago

























              answered yesterday









              P.WP.W

              16k31455




              16k31455













              • I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

                – Makhele Sabata
                21 hours ago













              • You are welcome.

                – P.W
                21 hours ago



















              • I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

                – Makhele Sabata
                21 hours ago













              • You are welcome.

                – P.W
                21 hours ago

















              I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

              – Makhele Sabata
              21 hours ago







              I worked with Python when i started learning programming, and it i had this functionality where you could pass the arguments by name. it would be nice if they had something like that in C++. Thanks for the answer I wasn't aware of the trailing arguments issue.

              – Makhele Sabata
              21 hours ago















              You are welcome.

              – P.W
              21 hours ago





              You are welcome.

              – P.W
              21 hours ago













              7














              In C++ you can only use (one or multiple) default parameters at the end of the parameter list. If you omit parameters in the middle, the compiler has no way of knowing, which argument belongs to which parameter. Therefore you have to specify the default parameters QLineEdit::Normal and QString() manually before passing &ok.



              In your not working case the compiler tries to match your bool pointer to the next type in the parameter list, which is QLineEdit::EchoMode and therefore not compatible.






              share|improve this answer




























                7














                In C++ you can only use (one or multiple) default parameters at the end of the parameter list. If you omit parameters in the middle, the compiler has no way of knowing, which argument belongs to which parameter. Therefore you have to specify the default parameters QLineEdit::Normal and QString() manually before passing &ok.



                In your not working case the compiler tries to match your bool pointer to the next type in the parameter list, which is QLineEdit::EchoMode and therefore not compatible.






                share|improve this answer


























                  7












                  7








                  7







                  In C++ you can only use (one or multiple) default parameters at the end of the parameter list. If you omit parameters in the middle, the compiler has no way of knowing, which argument belongs to which parameter. Therefore you have to specify the default parameters QLineEdit::Normal and QString() manually before passing &ok.



                  In your not working case the compiler tries to match your bool pointer to the next type in the parameter list, which is QLineEdit::EchoMode and therefore not compatible.






                  share|improve this answer













                  In C++ you can only use (one or multiple) default parameters at the end of the parameter list. If you omit parameters in the middle, the compiler has no way of knowing, which argument belongs to which parameter. Therefore you have to specify the default parameters QLineEdit::Normal and QString() manually before passing &ok.



                  In your not working case the compiler tries to match your bool pointer to the next type in the parameter list, which is QLineEdit::EchoMode and therefore not compatible.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered yesterday









                  AlbertMAlbertM

                  352210




                  352210























                      1














                      the error is beacuse of the optional paramteres:



                      QString QInputDialog::getText(
                      QWidget * parent,
                      const QString & title,
                      const QString & label,
                      QLineEdit::EchoMode mode = QLineEdit::Normal,
                      const QString& text = QString(),
                      bool * ok = 0,
                      Qt::WindowFlags flags = 0,
                      Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


                      QInputDialog::getText(
                      0,
                      "Enter an Address to Validate",
                      "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
                      --> QLineEdit::EchoMode ??
                      --> QString& text ??
                      &ok);


                      if you set one optional parameter, you have to set all the optional paramteters to the left of that, in your case QLineEdit::EchoMode and QString& text






                      share|improve this answer




























                        1














                        the error is beacuse of the optional paramteres:



                        QString QInputDialog::getText(
                        QWidget * parent,
                        const QString & title,
                        const QString & label,
                        QLineEdit::EchoMode mode = QLineEdit::Normal,
                        const QString& text = QString(),
                        bool * ok = 0,
                        Qt::WindowFlags flags = 0,
                        Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


                        QInputDialog::getText(
                        0,
                        "Enter an Address to Validate",
                        "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
                        --> QLineEdit::EchoMode ??
                        --> QString& text ??
                        &ok);


                        if you set one optional parameter, you have to set all the optional paramteters to the left of that, in your case QLineEdit::EchoMode and QString& text






                        share|improve this answer


























                          1












                          1








                          1







                          the error is beacuse of the optional paramteres:



                          QString QInputDialog::getText(
                          QWidget * parent,
                          const QString & title,
                          const QString & label,
                          QLineEdit::EchoMode mode = QLineEdit::Normal,
                          const QString& text = QString(),
                          bool * ok = 0,
                          Qt::WindowFlags flags = 0,
                          Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


                          QInputDialog::getText(
                          0,
                          "Enter an Address to Validate",
                          "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
                          --> QLineEdit::EchoMode ??
                          --> QString& text ??
                          &ok);


                          if you set one optional parameter, you have to set all the optional paramteters to the left of that, in your case QLineEdit::EchoMode and QString& text






                          share|improve this answer













                          the error is beacuse of the optional paramteres:



                          QString QInputDialog::getText(
                          QWidget * parent,
                          const QString & title,
                          const QString & label,
                          QLineEdit::EchoMode mode = QLineEdit::Normal,
                          const QString& text = QString(),
                          bool * ok = 0,
                          Qt::WindowFlags flags = 0,
                          Qt::InputMethodHints inputMethodHints = Qt::ImhNone)


                          QInputDialog::getText(
                          0,
                          "Enter an Address to Validate",
                          "Adress: comma separated (e.g Address line 1, Address line 2, City, Postal Code)",
                          --> QLineEdit::EchoMode ??
                          --> QString& text ??
                          &ok);


                          if you set one optional parameter, you have to set all the optional paramteters to the left of that, in your case QLineEdit::EchoMode and QString& text







                          share|improve this answer












                          share|improve this answer



                          share|improve this answer










                          answered yesterday









                          ΦXocę 웃 Пepeúpa ツΦXocę 웃 Пepeúpa ツ

                          33.8k113965




                          33.8k113965






























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