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  4. [Solved] Exporting functions and constants from C++ to QML

[Solved] Exporting functions and constants from C++ to QML

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  • I Offline
    I Offline
    Ices_Eyes
    wrote on last edited by
    #8

    Well... It worksss!!! Thaks guys ;)

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    • sierdzioS Offline
      sierdzioS Offline
      sierdzio
      Moderators
      wrote on last edited by
      #9

      I'm happy to hear that :) And you even marked the thread as solved - perfection itself. Happy further coding.

      (Z(:^

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      • I Offline
        I Offline
        Ices_Eyes
        wrote on last edited by
        #10

        Ok, I have one more question with respect to this :)
        What I have done is something like:
        @Q_INVOKABLE QString getUrl(QString urlParameter);@

        But in many tutorials I have seen now, the use
        @Q_INVOKABLE QString getNewsUrl(const QString &urlParameter);@

        Which one is more correct?

        Also. Having javascript "var" variables that contains integers, is there a way to pass this types to C++ instead of strings? Or should I convert them in C++? I mean... Using
        @Q_INVOKABLE QString getNewsUrl(int urlParameter);@
        gives me no right values in urlParameter variables...

        :)

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        • A Offline
          A Offline
          andre
          wrote on last edited by
          #11

          [quote author="Ices_Eyes" date="1346753251"]Ok, I have one more question with respect to this :)
          What I have done is something like:
          @Q_INVOKABLE QString getUrl(QString urlParameter);@

          But in many tutorials I have seen now, the use
          @Q_INVOKABLE QString getNewsUrl(const QString &urlParameter);@

          Which one is more correct?
          [/quote]
          Why would you assume the one is 'more' correct than the other. By what measure exactly?

          Some coding guidelines tell you to use const references for function arguments that as used unchanged by the function, and in that context using the const QString& might be more correct. But not everybody uses this guideline. For efficieny, there is very little gain here, as QString is implicitly shared and thus very fast to copy as a value.

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          • sierdzioS Offline
            sierdzioS Offline
            sierdzio
            Moderators
            wrote on last edited by
            #12

            [quote author="Ices_Eyes" date="1346753251"]
            Also. Having javascript "var" variables that contains integers, is there a way to pass this types to C++ instead of strings? Or should I convert them in C++? I mean... Using
            @Q_INVOKABLE QString getNewsUrl(int urlParameter);@
            gives me no right values in urlParameter variables...
            :)[/quote]

            As Andre already covered the top part, I'll take on the bottom one. QML automatically translates JS values to C++ ones. So, for int you get c++ int, for real you get Qt's qreal, for string it's QString, for arrays is complicated (as you can store anything there. But basically QObjectList tends to work in most cases, or QVariantList etc.). There is no need for conversion of those basic types.

            (Z(:^

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            • I Offline
              I Offline
              Ices_Eyes
              wrote on last edited by
              #13

              So, I need to understand why
              @
              var parameter = 1;
              ...
              myClass.myFunc(parameter)
              @
              works if myFunct is defined with QString and does not work if defined with int... ;)

              Thanks guys!!! :)

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              • I Offline
                I Offline
                Ices_Eyes
                wrote on last edited by
                #14

                Damn!!! My bad... It was a conversion problem in C++ of integer to string!!! Damn, too much codin in Java and Javascript, I have completly forgotten C!!! :(

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                • sierdzioS Offline
                  sierdzioS Offline
                  sierdzio
                  Moderators
                  wrote on last edited by
                  #15

                  This is indeed strange. Be sure to make a full app rebuild (clean, run qmake, build) just to make sure that MOC updates the definitions. It quite definitely works for me. Alternatively, you can try using QVariant in c++ declaration, and then calling ::toInt() on the value - but that should not be necessary.

                  (Z(:^

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                  • I Offline
                    I Offline
                    Ices_Eyes
                    wrote on last edited by
                    #16

                    Solved with a QString::number(parameter)...

                    Damn me... :P

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                    • sierdzioS Offline
                      sierdzioS Offline
                      sierdzio
                      Moderators
                      wrote on last edited by
                      #17

                      Happens to everybody :) That took me by surprise a few times, too. I tend to forget about ::number() especially when I'm tired and after prolonged QML-only phases :D

                      (Z(:^

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