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Reading .txt file info into variables

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  • S Offline
    S Offline
    sheehan1234
    wrote on last edited by
    #1

    How do I read in a text file and assign the integers in that file to my own variables?

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    • G Offline
      G Offline
      giesbert
      wrote on last edited by
      #2

      That depends, as always :-)
      I have no oidea, how the structure of the file is.
      Let's gess, one line contains one integer.
      Then you could just read the whole file into a QStringList, iterate of the entries and call toINt on each of them.

      Nokia Certified Qt Specialist.
      Programming Is Like Sex: One mistake and you have to support it for the rest of your life. (Michael Sinz)

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      • S Offline
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        sheehan1234
        wrote on last edited by
        #3

        Thank you very much Gerolf. I found this code snippet which supposedly puts my text file into a QStringList

        @QStringList stringList;
        QFile textFile("test.txt");
        QTextStream textStream(&textFile);
        while (true)
        {
        QString line = textStream.readLine();
        if (line.isNull())
        break;
        else
        stringList.append(line);
        }@

        If that is done correctly, how do I go about iterating through it?

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        • S Offline
          S Offline
          sheehan1234
          wrote on last edited by
          #4

          I have QStringList of integers that I read in from a file. How do I iterate through this list to: a) save each value b) cast each to an integer.

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          • M Offline
            M Offline
            mlong
            wrote on last edited by
            #5

            I'm not sure what you mean by "save each value" but iterating through a QStringList is fairly simple. There are a number of ways to do so.

            @
            QStringList list;

            // iterate through each element of list (which will be accessible via the QString "str")
            foreach (QString str, list)
            {
            ...
            int value = str.toInt(); // get integer representation of str
            ...
            }
            @

            BTW, This stuff is very well-documented.

            Software Engineer
            My views and opinions do not necessarily reflect those of anyone -- living or dead, real or fictional -- in this universe or any other similar multiverse node. Void where prohibited. Your mileage may vary. Caveat emptor.

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            • S Offline
              S Offline
              sheehan1234
              wrote on last edited by
              #6

              I meant to say store each into a variable, which you answered. However I'm trying to do so in the following code, and when I try to print the value, nothing is displayed. Am I reading my text file into the QStringList incorrectly?

              @int main()
              {
              QStringList stringList;
              QFile textFile("test.txt");
              QTextStream textStream(&textFile);
              while (true)
              {
              QString line = textStream.readLine();
              if (line.isNull())
              break;
              else
              stringList.append(line);
              }

              foreach(QString str, stringList)
              {
                  int value = str.toInt();
                  cout << value;
              }
              return 0;
              

              }
              @

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              • M Offline
                M Offline
                mlong
                wrote on last edited by
                #7

                You need to call "textFile.open()":http://doc.qt.nokia.com/4.7-snapshot/qfile.html#open

                Be sure and check its return value. There's an example in the QFile docs.

                Software Engineer
                My views and opinions do not necessarily reflect those of anyone -- living or dead, real or fictional -- in this universe or any other similar multiverse node. Void where prohibited. Your mileage may vary. Caveat emptor.

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                • M Offline
                  M Offline
                  mlong
                  wrote on last edited by
                  #8

                  A cleaner implementation would probably be:

                  @
                  QStringList stringList;
                  QFile textFile("test.txt");
                  if (textFile.open(QIODevice::ReadOnly)
                  {
                  QTextStream textStream(&textFile);
                  while (!textStream.atEnd())
                  {
                  stringList.append(textStream.readLine());
                  }
                  }
                  @

                  Caveat: Brain to keyboard. Untested code. Not responsible for silly errors. YMMV

                  Software Engineer
                  My views and opinions do not necessarily reflect those of anyone -- living or dead, real or fictional -- in this universe or any other similar multiverse node. Void where prohibited. Your mileage may vary. Caveat emptor.

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                  • S Offline
                    S Offline
                    sheehan1234
                    wrote on last edited by
                    #9

                    that worked! thank you very much!

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                    • G Offline
                      G Offline
                      goetz
                      wrote on last edited by
                      #10

                      [quote author="sheehan1234" date="1317152090"]
                      If that is done correctly, how do I go about iterating through it?[/quote]

                      @
                      foreach(const QString line, stringList) {
                      // do something with the line
                      }
                      @

                      http://www.catb.org/~esr/faqs/smart-questions.html

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

                        This discussion looks a lot like "this":http://developer.qt.nokia.com/forums/viewthread/10146/ one...

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                        • G Offline
                          G Offline
                          goetz
                          wrote on last edited by
                          #12

                          [quote author="Andre" date="1317189187"]This discussion looks a lot like "this":http://developer.qt.nokia.com/forums/viewthread/10146/ one...[/quote]

                          I merged both threads.

                          http://www.catb.org/~esr/faqs/smart-questions.html

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                          • S Offline
                            S Offline
                            sheehan1234
                            wrote on last edited by
                            #13

                            I have the code exactly as you all have showed me but there was no output. so i put some print statements inside of the loops to see if the compiler was even entering the loops and it is not. What am I doing wrong?

                            @int main()
                            {
                            QStringList stringList;
                            QFile textFile("test.txt");
                            if (textFile.open(QIODevice::ReadOnly))
                            {
                            QTextStream textStream(&textFile);
                            while (!textStream.atEnd())
                            {
                            stringList.append(textStream.readLine());
                            cout << "test1";
                            }
                            }
                            foreach(const QString line, stringList)
                            {
                            cout << "test2";
                            cout << line.toStdString();
                            }
                            return 0;
                            }@

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                            • V Offline
                              V Offline
                              vsorokin
                              wrote on last edited by
                              #14

                              Are you sure that your test.txt are in same directory that your executable file?

                              --
                              Vasiliy

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                              • M Offline
                                M Offline
                                mlong
                                wrote on last edited by
                                #15

                                You should print an error message if it cannot open the file.
                                @
                                if (...open...)
                                {
                                ...
                                }
                                else
                                {
                                // tell me about it
                                }
                                @

                                Software Engineer
                                My views and opinions do not necessarily reflect those of anyone -- living or dead, real or fictional -- in this universe or any other similar multiverse node. Void where prohibited. Your mileage may vary. Caveat emptor.

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