Qt QFileSystemWatcher Example - Watch a directory and do some processing if it is changed with QEventLoop

qt_directory_watcher.cpp

// ----------------------------------------------
// List the contents of a directory if changed
// Using QFileSystemWatcher, QDirIterator and
// QEventLoop, and lambda function for connect
// ----------------------------------------------

#include <QObject>
#include <QEventLoop>
#include <QDebug>
#include <QFileSystemWatcher>
#include <QDirIterator>

void listDirectoryContents( const QString& dir ) noexcept
{
    QFileSystemWatcher watcher;
    watcher.addPath( dir );

    QEventLoop loop;
    
    QObject::connect( &watcher, &QFileSystemWatcher::directoryChanged,
                      []( const QString& path )
    {
        QDirIterator it( path,
                        { "*.txt" },        // Filter: *.txt  
                        QDir::AllFiles );   // Files only

        while ( it.hasNext() )              // List all txt files
        {                                   // on console
            qDebug() << it.next();
        }
    });
    
    QObject::connect( &watcher, &QFileSystemWatcher::directoryChanged,
                      &loop, &QEventLoop::quit );
    
    loop.exec();
}

// Example

int main()
{
    const QString dir { "C:/Watchable" };
    listDirectoryContents( dir );
    return 0;
}