Wrong Implementation of single instance application

AyushExel204

@VRonin yes they are same

VRonin

What's the output of mSocket->readAll() ? could you paste it here?

P.S.

playlist->addMedia(QUrl::fromLocalFile(QString(mSocket->readAll())); // no need to use STD string

SingleInstance(QObject *parent = 0, QMediaPlaylist* pl=new QMediaPlaylist /*<- This is horrible and 99% memory leak guaranteed*/);

AyushExel204

@VRonin Okay so I selected the 10 audio files and pressed "Enter" and printed the output of mSocket->readAll() . The output is :

D:\Music\songs\5 second of summer\5 Seconds Of Summer\08 - End Up Here - (www.SongsLover.pk).mp3
D:\Music\songs\5 second of summer\5 Seconds Of Summer\12 - Amnesia - (www.SongsLover.pk).mp3







D:\Music\songs\5 second of summer\5 Seconds Of Summer\Voodoo Doll.mp3

So it is clear that only 3 files are added in the playlist and the address of other files are just replaced by a new line.

VRonin

I suspect it has to do with encoding

try replacing buffer.append(arg); with

QDataStream out(&buffer,QIODevice::WriteOnly);
out << arg;

and replace playlist->addMedia(QUrl::fromLocalFile(QString::fromStdString(mSocket->readAll().toStdString()))); with

const QByteArray buffer=mSocket->readAll();
QDataStream in(buffer);
QString argString;
in >> argString;
playlist->addMedia(QUrl::fromLocalFile(argString);

and check that argString has all the lines in it

AyushExel204

@VRonin Okay so now even when I open a single media file , it is not added in the playlist . So, I have reverted back to the original code. I want to add that, sometimes the program works correctly and all media files that I select are added in the playlist but most of the times few of them are not added , instead just a blank line is added in the playlist.

kshegunov

@AyushExel204

You're overwriting the socket pointer when multiple connections are pending

mSocket = mServer.nextPendingConnection();
connect(mSocket,SIGNAL(readyRead()),this,SLOT(readyRead()));

Then you read from incorrect socket(s):

playlist->addMedia(QUrl::fromLocalFile(QString::fromStdString(mSocket->readAll().toStdString())));

Try this:

void SingleInstance::readyRead()
{ 
    QLocalSocket * socket = qobject_cast<QLocalSocket *>(sender());
    playlist->addMedia(QUrl::fromLocalFile(socket->readAll()));
    // ...
    socket->deleteLater();
}

Also I don't understand why you insist on converting QString to std::string and then back again??!

VRonin

I still think that if the file path contains non-ASCII this implementation will fail as it converts from QString to QByteArray with no checks

kshegunov

@VRonin

I still think that if the file path contains non-ASCII this implementation will fail as it converts from QString to QByteArray with no checks

~~Yes, it's quite possible.~~
Actually it turns out the QString is implicitly converted to utf8 and then added to the byte array. So it might actually work.

AyushExel204

@kshegunov said:

QLocalSocket * socket = qobject_cast<QLocalSocket *>(sender());
playlist->addMedia(QUrl::fromLocalFile(socket->readAll()));

Thanks .. this fixed my problem . but can you explain what this code does ?

jsulm

sender() returns the pointer to the object which emitted the signal (http://doc.qt.io/qt-5.6/qobject.html#sender).
In this case it is a pointer to QLocalSocket, so you need to cast it from QObject* to QLocalSocket* using qobject_cast