Results 1 to 3 of 3

Thread: Sorting a QList

  1. #1
    Join Date
    Apr 2020
    Posts
    14
    Qt products
    Qt5
    Platforms
    Unix/X11

    Default Sorting a QList

    Hallo,

    in my app the user has the possibility to add a station to a QListWidget. This works very well. After adding the station the list has to be updated. The problem, the QListWidget reads the stations and its frequency from a txt file.

    So i need to sort the stations in the txt file not in the QListWidget, as I use the row index to tune to the station.

    How can I sort the output before it is saved to the txt file?

    The strings to campore look something like:

    Jump,105600000
    Station 1 93 MHz,93000000
    man station@ 101.2MHz,101200000

    Qt Code:
    1. ui->btn_rename->setVisible(true);
    2.  
    3. QString add_station = ui->ln_man_tune->text();
    4. float add_station_float = add_station.toFloat();
    5. int multi = add_station_float * 1000000;
    6. QString station_conv_string = (QString::number(multi));
    7.  
    8. if(!add_station.isEmpty()){
    9. QFile out_tmp("../tmp.txt");
    10. QFile file_fm(path_fm);
    11.  
    12. if(!file_fm.open(QFile::ReadOnly | QFile::Text)){
    13. return;
    14. }
    15.  
    16. if(!out_tmp.open(QFile::WriteOnly | QFile::Text)){
    17. return;
    18. }
    19.  
    20. QTextStream in_file_fm(&file_fm);
    21. file_fm.resize(0);
    22. QTextStream out(&out_tmp);
    23. QStringList unsort_scan_fm;
    24.  
    25. while(!in_file_fm.atEnd()){
    26. QString line = in_file_fm.readLine();
    27.  
    28. QString outline = line;
    29.  
    30. unsort_scan_fm.append(outline);
    31. }
    32.  
    33. if(add_station.contains(",")){
    34. add_station = add_station.replace(",", ".");
    35. }
    36. if(!add_station.contains(".")){
    37. add_station = add_station.append(".0");
    38. }
    39.  
    40. //add new station at end of file
    41. QString outline = "man station@ " + add_station + "MHz," + station_conv_string;
    42.  
    43. unsort_scan_fm.append(outline);
    44. qDebug() << "before sort: :" << unsort_scan_fm;
    45.  
    46. std::sort(unsort_scan_fm.begin(), unsort_scan_fm.end());
    47.  
    48. qDebug() << "after sort: :" << unsort_scan_fm;
    49.  
    50. foreach(QString after_sort, unsort_scan_fm){
    51. out << after_sort << "\n";
    52. }
    53.  
    54. file_fm.close();
    55. out_tmp.flush();
    56. out_tmp.close();
    57.  
    58. file_fm.remove();
    59. out_tmp.rename(path_fm);
    60.  
    61. ui->ls_fm->clear();
    62.  
    63. MainWindow::fill_list();
    64. MainWindow::fm_list();
    65. }
    To copy to clipboard, switch view to plain text mode 

    Debug before sort and after sort are the same:

    Qt Code:
    1. after sort: : ("Jump,105600000", "Station 1 93 MHz,93000000", "Station 3 98.1 MHz,98100000", "Station 4 99.9 MHz,99900000", "Top40,94800000", "any station,107600000", "man station@ 100.2MHz,100200000", "man station@ 101.2MHz,101200000", "man station@ 101.3MHz,101300000", "man station@ 101.3MHz,101300000", "man station@ 104.6MHz,104600000", "man station@ 105.3MHz,105300000", "man station@ 105.4MHz,105400000", "man station@ 111.1MHz,111100000", "man station@ 96.8MHz,96800000", "man station@ 97.8MHz,97800000", "man station@ 99.9MHz,99900000", "zulu station,100700000")
    To copy to clipboard, switch view to plain text mode 
    Last edited by vitalic; 28th April 2020 at 20:15.

  2. #2
    Join Date
    Mar 2009
    Location
    Brisbane, Australia
    Posts
    7,729
    Thanks
    13
    Thanked 1,610 Times in 1,537 Posts
    Qt products
    Qt4 Qt5
    Platforms
    Unix/X11 Windows
    Wiki edits
    17

    Default Re: Sorting a QList

    Quote Originally Posted by vitalic View Post
    Hallo,
    Qt Code:
    1. after sort: : ("Jump,105600000", "Station 1 93 MHz,93000000", "Station 3 98.1 MHz,98100000", "Station 4 99.9 MHz,99900000", "Top40,94800000", "any station,107600000", "man station@ 100.2MHz,100200000", "man station@ 101.2MHz,101200000", "man station@ 101.3MHz,101300000", "man station@ 101.3MHz,101300000", "man station@ 104.6MHz,104600000", "man station@ 105.3MHz,105300000", "man station@ 105.4MHz,105400000", "man station@ 111.1MHz,111100000", "man station@ 96.8MHz,96800000", "man station@ 97.8MHz,97800000", "man station@ 99.9MHz,99900000", "zulu station,100700000")
    To copy to clipboard, switch view to plain text mode 
    That looks like a case-sensitive string sort to me. Jump sorts before Station 1, which sorts before Station3 etc.

    Were you expecting it to be sorted ignoring case, i.e. "any station,107600000", Jump ... then man ..., or to sort numerically on frequency?

    Take a look at QStringList::sort() if you intended a case-insensitive string sort.
    If you wanted a numeric sort then you have more work to do.

  3. #3
    Join Date
    Apr 2020
    Posts
    14
    Qt products
    Qt5
    Platforms
    Unix/X11

    Default Re: Sorting a QList

    I fixed the sort problem with this function:

    Qt Code:
    1. QStringList MainWindow::sort_list(QStringList list){
    2.  
    3. QCollator coll;
    4. coll.setNumericMode(true);
    5.  
    6. std::sort(list.begin(), list.end(), [&](const QString& s1, const QString& s2){ return coll.compare(s1, s2) < 0; });
    7.  
    8. return list;
    9. }
    To copy to clipboard, switch view to plain text mode 

Similar Threads

  1. Sorting using qSort(), - if QList contains POINTERS
    By joseph in forum Qt Programming
    Replies: 13
    Last Post: 18th August 2013, 19:55
  2. sorting QList<double>
    By timmu in forum Qt Programming
    Replies: 7
    Last Post: 24th August 2012, 17:35
  3. sorting QList<float>
    By timmu in forum Newbie
    Replies: 2
    Last Post: 23rd January 2012, 18:16
  4. sorting static QList<MyClass> list with qSort
    By oruccim in forum Qt Programming
    Replies: 3
    Last Post: 15th December 2010, 17:13
  5. Replies: 5
    Last Post: 18th December 2008, 14:58

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Digia, Qt and their respective logos are trademarks of Digia Plc in Finland and/or other countries worldwide.