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QFile Problem

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  • L LainOnTheWired

    I try to write a file with the QFile library with the following code like it is in the QT documentation..

    QFile file("out.txt");
        if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
            return;
    
        QTextStream out(&file);
        out << "The magic number is: " << 49 << "\n";
    

    But it complains about the file.open part.

    J.HilkJ Offline
    J.HilkJ Offline
    J.Hilk
    Moderators
    wrote on last edited by
    #2

    @LainOnTheWired said in QFile Problem:

    But it complains about the file.open part.

    you need to be more specific


    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
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    • L Offline
      L Offline
      LainOnTheWired
      wrote on last edited by LainOnTheWired
      #3

      It says canditate function not vaible: no knowen conversation from int to OpenMode(aka QFlags<QIODevice OpenModeFlag>) for 1st argument. Is this enough or do you need more ?

      J.HilkJ 1 Reply Last reply
      0
      • L LainOnTheWired

        It says canditate function not vaible: no knowen conversation from int to OpenMode(aka QFlags<QIODevice OpenModeFlag>) for 1st argument. Is this enough or do you need more ?

        J.HilkJ Offline
        J.HilkJ Offline
        J.Hilk
        Moderators
        wrote on last edited by
        #4

        @LainOnTheWired
        did you include QFile ?

        #include <QFile>


        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
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        • L Offline
          L Offline
          LainOnTheWired
          wrote on last edited by
          #5

          Yes it is included.

          1 Reply Last reply
          0
          • VRoninV Offline
            VRoninV Offline
            VRonin
            wrote on last edited by
            #6

            very strange... in any case you can replace

            if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
                    return;
            

            with

            if (!file.open(QIODevice::WriteOnly))
                    return;
            file.setTextModeEnabled(true);
            

            "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
            ~Napoleon Bonaparte

            On a crusade to banish setIndexWidget() from the holy land of Qt

            JonBJ 1 Reply Last reply
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            • VRoninV VRonin

              very strange... in any case you can replace

              if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
                      return;
              

              with

              if (!file.open(QIODevice::WriteOnly))
                      return;
              file.setTextModeEnabled(true);
              
              JonBJ Online
              JonBJ Online
              JonB
              wrote on last edited by
              #7

              @VRonin
              I'd be worried if I got his error message! I don't do C++/includes, but does he need to also #include <QIODevice> for the flag definitions?

              VRoninV 1 Reply Last reply
              1
              • L Offline
                L Offline
                LainOnTheWired
                wrote on last edited by LainOnTheWired
                #8

                Yes thats it with include<QIODevice> it works thanks so much :) and you need to include #include <qtextstream.h> for the stream too.

                JKSHJ 1 Reply Last reply
                0
                • L LainOnTheWired

                  Yes thats it with include<QIODevice> it works thanks so much :) and you need to include #include <qtextstream.h> for the stream too.

                  JKSHJ Offline
                  JKSHJ Offline
                  JKSH
                  Moderators
                  wrote on last edited by
                  #9

                  @LainOnTheWired said in QFile Problem:

                  Yes thats it with include<QIODevice> it works thanks so much :) and you need to include #include <qtextstream.h> for the stream too.

                  That's very odd. The QFile header should already contain #include <QIODevice>...

                  Has the QFile header been modified?

                  Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

                  1 Reply Last reply
                  4
                  • JonBJ JonB

                    @VRonin
                    I'd be worried if I got his error message! I don't do C++/includes, but does he need to also #include <QIODevice> for the flag definitions?

                    VRoninV Offline
                    VRoninV Offline
                    VRonin
                    wrote on last edited by
                    #10

                    @JonB said in QFile Problem:

                    I'd be worried if I got his error message!

                    I wouldn't. It just cannot find the operator|() that is defined as part of specialising QFlags. Not a big deal

                    "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
                    ~Napoleon Bonaparte

                    On a crusade to banish setIndexWidget() from the holy land of Qt

                    JonBJ 1 Reply Last reply
                    2
                    • VRoninV VRonin

                      @JonB said in QFile Problem:

                      I'd be worried if I got his error message!

                      I wouldn't. It just cannot find the operator|() that is defined as part of specialising QFlags. Not a big deal

                      JonBJ Online
                      JonBJ Online
                      JonB
                      wrote on last edited by
                      #11

                      @VRonin
                      That's precisely what I meant! Perhaps "worried" was too strong a word :) The error message suggested to me that the QFlags were not working correctly with the | operator, hence my guess about not having the correct #include. I intended to suggest that the OP should pursue why this appeared to be the case.

                      1 Reply Last reply
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                      • L Offline
                        L Offline
                        LainOnTheWired
                        wrote on last edited by LainOnTheWired
                        #12

                        It is the fault of KDevelop, if i have only the QFile include it puts this error message but if i compile the program it works correctly. The error message is wrong. Very strange and no i have not modified the header file.

                        JonBJ 1 Reply Last reply
                        0
                        • L LainOnTheWired

                          It is the fault of KDevelop, if i have only the QFile include it puts this error message but if i compile the program it works correctly. The error message is wrong. Very strange and no i have not modified the header file.

                          JonBJ Online
                          JonBJ Online
                          JonB
                          wrote on last edited by
                          #13

                          @LainOnTheWired

                          The error message is wrong.

                          Up to you, but the compiler error/warning message cannot be "wrong". If it warns it means what it says in terms of not having the definition, compilers don't invent error messages. It may work at runtime if it's only a warning and the semantics actually allow an int operator|() to work in this case, which it probably does.

                          Likely perhaps: if you have other #includes (e.g. from "KDevelop") prior (or possibly post) to your #include <QFile> that might affect definitions/behaviour and cause your issue....

                          jsulmJ 1 Reply Last reply
                          0
                          • JonBJ JonB

                            @LainOnTheWired

                            The error message is wrong.

                            Up to you, but the compiler error/warning message cannot be "wrong". If it warns it means what it says in terms of not having the definition, compilers don't invent error messages. It may work at runtime if it's only a warning and the semantics actually allow an int operator|() to work in this case, which it probably does.

                            Likely perhaps: if you have other #includes (e.g. from "KDevelop") prior (or possibly post) to your #include <QFile> that might affect definitions/behaviour and cause your issue....

                            jsulmJ Online
                            jsulmJ Online
                            jsulm
                            Lifetime Qt Champion
                            wrote on last edited by
                            #14

                            @JonB I think the error is not coming from the compiler but from the Clang Code Model which is known for producing many false positives.
                            @LainOnTheWired You can try to disable Clang Code Model

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

                            JonBJ 1 Reply Last reply
                            1
                            • jsulmJ jsulm

                              @JonB I think the error is not coming from the compiler but from the Clang Code Model which is known for producing many false positives.
                              @LainOnTheWired You can try to disable Clang Code Model

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

                              @jsulm
                              Ohhh, I don't know anything about CLang or that the OP is using that, apologies then if my comment was misleading.

                              jsulmJ 1 Reply Last reply
                              0
                              • JonBJ JonB

                                @jsulm
                                Ohhh, I don't know anything about CLang or that the OP is using that, apologies then if my comment was misleading.

                                jsulmJ Online
                                jsulmJ Online
                                jsulm
                                Lifetime Qt Champion
                                wrote on last edited by
                                #16

                                @JonB No problem! Actually the OP was not clear when saying "it puts this error message" - this can be the compiler or the code model.

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

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