How can i write any data on directory

[Armin]

Hi
Look at the code please :

void MainWindow::on_pushButton_clicked()
{
QNetworkAccessManager *netaccessmanager;
QNetworkReply *netreply = netaccessmanager->get(QNetworkRequest(QUrl(ui->textEdit->toPlainText())));

}

I have two question :

1- Asked data that is returned where will stored in *netreply?

2- How can i write any data on directory ? ( like c:/armin/download )
Which member in QIOdevice i should use?

[mrjj]

Hi
1 - it will send a signal when something is read (replyFinished) or error happened.
void getDoc::on_pushButton_2_clicked()
{
manager = new QNetworkAccessManager(this);
connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));
manager->get(QNetworkRequest(QUrl("http://www.google.com")));
}

void getDoc::replyFinished(QNetworkReply *reply)
{
// qDebug() << reply->error();
QByteArray data=reply->readAll();
}

2-
use QFile and qdatastream to save it to a file.

[Xiami]

    auto reply = Manager.get(QNetworkRequest(QUrl("...")));
    connect(reply,&QNetworkReply::finished,this,[&]{
        auto array = ((QNetworkReply*)sender())->readAll();
        sender()->deleteLater();
        if(array.isEmpty())return;
        QFile file(QCryptographicHash::hash(array,QCryptographicHash::Md5));
        if(file.open(QIODevice::WriteOnly)){
            file.write(array);
            file.close();
        }
    });

[Armin]

@mrjj said in How can i write any data on directory:

connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));

Can you more explain for that?
I can't understand

[mrjj]

@Armin

Connect connect from a signal to a slot(function)

so here it says
When the manager say "finished" then call replyFinished located in "this" object

connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));

and the slot / function us
void mainwindow::replyFinished(QNetworkReply *reply)

So all it does is to set up the connect for a signal and which function we want it to call.

so say we have 2 classes

A and B
A has beep signal and B have beepHandler
then we say
connect( pointer to a, beep , pointer to b, beephandler )
so beep goes to beephandler

For more info , please see
http://doc.qt.io/qt-5/signalsandslots.html

The version @Xiami is using just the same, but he uses the new syntax and
uses a lambda which is a c++ things that allows you to define functions in place/right there.
connect(reply,&QNetworkReply::finished,this,[&] { this is your slot }

[Armin]

@mrjj Thanks
Why in this example you have pointed to class?

[mrjj]

@Armin
because connects wants the address of a real objects.
like in
ClassX * inst= new ClassX;
inst is the right kind for connect.
Its a instance of the type/class ClassX;

Its not for all ClassX created, but only
for those you connect.

[Armin]

@mrjj I feel, your code is hard and twisted , so can you make it simpler for me?

[VRonin]

@Armin said in How can i write any data on directory:

your code is hard and twisted

No it's not, I wouldn't know how to make it easier. You should probably take a look at http://doc.qt.io/qt-5/signalsandslots.html

---

@Xiami

• no need to use the "controversial" sender() here, just pass reply by value in the capturing group of the lambda
• do not use C-cast to downcast, it's unsafe, use dynamic_cast or, if it's a QObject as it's always the case when calling sender(), qobject_cast
• if the downloaded file is too big you might run out of memory if you wait for finished do the processing as soon as there is data available using readyRead

QFile* file=new QFile("DownloadResult.dat"); //the file to save the data into
if(file->open(QIODevice::WriteOnly)){ //if you can open the file for writing
    QNetworkAccessManager *netaccessmanager = new QNetworkAccessManager; //create the manager
    QNetworkReply* reply = netaccessmanager.get(QNetworkRequest(QUrl(ui->textEdit->toPlainText()))); // send the request
    connect(reply,&QNetworkReply::readyRead,this,[reply,file]()->void{ //when there is data available
        file->write(reply->readAll()); //save it to file
    });
    connect(reply,&QNetworkReply::finished,reply,&QNetworkReply::deleteLater); //when finished clear the memory
    connect(netaccessmanager,&QNetworkAccessManager::finished,reply,&QNetworkAccessManager::deleteLater); //when finished clear the memory
    connect(reply,&QNetworkReply::finished,file,&QFile::deleteLater);//when finished close the file and clear the memory
}

[Armin]

@mrjj said in How can i write any data on directory:

connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));
manager->get(QNetworkRequest(QUrl("http://www.google.com")));

why connect is on 5 line ?
shouldn't be on 4 line?

[mrjj]

@Armin
Hi
well its just important to connect it up before starting to use it.
So best spot is usual when you create it.

[Armin]

@mrjj
Can i use code in below?

QNetworkRequest request;
request.setUrl(QUrl("http://qt-project.org"));
request.setRawHeader("User-Agent", "MyOwnBrowser 1.0");

QNetworkReply *reply = manager->get(request);
connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));

[mrjj]

@Armin
Yes looks fine :)

[Armin]

@mrjj said in How can i write any data on directory:

1 - it will send a signal when something is read (replyFinished) or error happened.

I get this message :
QObject::connect: No such signal QNetworkAccessManager::finished(*QNetworkReply) in ..\DownloadManager\mainwindow.cpp:20
QObject::connect: (receiver name: 'MainWindow')

why?

[mrjj]

show the actual real code
it says QNetworkAccessManager dont have finished signal but syntax looks wrong

QNetworkAccessManager::finished(*QNetworkReply) <<< the * seems very wrong