c++ - 如何只将新文本写入文本文件

Question

我正在尝试编写一个 C++ 应用程序，它只会写入尚未包含在文本文件中的新文本，但到目前为止我无法让我的实现无法正常工作。即使文本已经包含，文本也会写入文本文件。

我做错了什么？

以下是我到目前为止的实现。

void ScanDir::qDirIteratorScanner()
{
    QDirIterator it(this -> basePath, QDir::Files, QDirIterator::Subdirectories);
    while (it.hasNext())
    {
        paths = scanned();

        qDebug() << "Collected : " << paths.size();

        if (!paths.contains(it.next())) {
            WriteToFile writeToFile(basePath, it.next());
            paths << it.next();
        }
        else {
            qDebug() << "Already put : " << it.next();
        }
    }

}  

---

QStringList ScanDir::scanned()
{
    QStringList paths;

    QFile dataFile(basePath + "data.txt");
    QTextStream in (&dataFile);

    if (dataFile.open(QIODevice::ReadOnly))
    {
        QTextStream in(&dataFile);

        while (!in.atEnd())
        {
            QString line = in.readLine();
            paths << line;
        }

        dataFile.close();
    }

    return paths;
}  

---

WriteToFile::WriteToFile(QString path, QString data)
{
    path = "E:/Data.txt";
    QFile file(path);
    if ( file.open(QFile::Append) )
    {
        QTextStream stream( &file );
        stream << data << endl;
        qDebug() << "Writting: " << data + "\r\n";

    }
}

Answer 1

每次迭代你应该只调用 it.next() 一次: http://doc.qt.io/qt-5/qdiriterator.html#next

Advances the iterator to the next entry, and returns the file path of this new entry. If hasNext() returns false, this function does nothing, and returns an empty QString.

You can call fileName() or filePath() to get the current entry file name or path, or fileInfo() to get a QFileInfo for the current entry.