Question

好的，我正在尝试对自己的TvShow类列表进行排序，以按用户决定的顺序显示TvShows列表。这是我在阅读qSort（）的文档后到目前为止所提出的。

bool MainWindow::compareShowsByName(TvShow* showA, TvShow* showB)
{
    return showA->getShowName() < showB->getShowName();
}

QList<TvShow*> MainWindow::orderShowsByName()
{
    QList<TvShow*> orderedShowList = appSettings.TvShows;
    qSort(orderedShowList.begin(), orderedShowList.end(), compareShowsByName);
    return orderedShowList;
}

当然，这会失败并出现以下错误：

../EpisodeNext/mainwindow.cpp: In member function 'QList<TvShow*> MainWindow::orderShowsByName()':
../EpisodeNext/mainwindow.cpp:192: error: no matching function for call to 'qSort(QList<TvShow*>::iterator, QList<TvShow*>::iterator, <unresolved overloaded function type>)'
../../QtSDK/Simulator/Qt/gcc/include/QtCore/qalgorithms.h:184: note: candidates are: void qSort(RandomAccessIterator, RandomAccessIterator, LessThan) [with RandomAccessIterator = QList<TvShow*>::iterator, LessThan = bool (MainWindow::*)(TvShow*, TvShow*)]
../EpisodeNext/mainwindow.cpp: In member function 'QList<TvShow*> MainWindow::orderShowsByAirDate()':
../EpisodeNext/mainwindow.cpp:199: error: no matching function for call to 'qSort(QList<TvShow*>::iterator, QList<TvShow*>::iterator, <unresolved overloaded function type>)'
../../QtSDK/Simulator/Qt/gcc/include/QtCore/qalgorithms.h:184: note: candidates are: void qSort(RandomAccessIterator, RandomAccessIterator, LessThan) [with RandomAccessIterator = QList<TvShow*>::iterator, LessThan = bool (MainWindow::*)(TvShow*, TvShow*)]
make: *** [mainwindow.o] Error 1

知道什么是错的吗？我正在使用最新版本的Qt SDK（Qt SDK 1.1 RC和Qt 4.7.3）

提前致谢！

Answer 1

罗宾，除了你需要在MainWindow.cpp文件中将“compareShowsByName”函数声明为全局之外，你做了一切正确的事情。所以像这样的代码编译并正常工作：

bool compareShowsByName(TvShow* showA, TvShow* showB)
{
    return showA->getShowName() < showB->getShowName();
}

QList<TvShow*> MainWindow::orderShowsByName()
{
    QList<TvShow*> orderedShowList = appSettings.TvShows;
    qSort(orderedShowList.begin(), orderedShowList.end(), compareShowsByName);
    return orderedShowList;
}

注意：除非您想在MainWindow外部（应用程序的任何其他部分）使用它，否则您不一定需要在MainWindow.h中声明“compareShowsByName”。但是，如果您仍想将“compareShowsByName”声明为MainWindow类的成员函数，则只需正确传递pointer to a member-function。

希望有所帮助。

为什么qSort（）不起作用？

1 个答案: