Storing data from QnetworkReply

[mrjj]

@LeeH said in Storing data from QnetworkReply:
Hi
If you keep the instance of class Downloader around,
there is no reason you cannot keep the data for later.
Say if you append to a QByteArray variable defined as
class member in Downloader

Can you please show the actual code how you use your helper class and how you later
try to access the data?

[LeeH]

@mrjj said in Storing data from QnetworkReply:

Can you please show the actual code how you use your helper class and how you later
try to access the data?

Certainly.

header:

class data : public QObject{

    Q_OBJECT

public:
    data();
    void download();
    QByteArray get();

public slots:

    void output(QNetworkReply* rep);

private:
    QNetworkAccessManager* _qnam;
    QByteArray _ba;

};

source:

data::data(){}

void data::download(){

    _qnam = new QNetworkAccessManager(this);
    _qnam->get(QNetworkRequest(QUrl("http://www.google.com")));
    QObject::connect(_qnam, SIGNAL(finished(QNetworkReply*)), this, SLOT(output(QNetworkReply*)));
}

void data::output(QNetworkReply* rep){

        if(!rep->error()){

           _ba.append(rep->readAll());

        }
        rep->deleteLater();
    }

QByteArray data::get(){
    qDebug() << _ba;
}

main:

 data obj;
 obj.download();
 obj.get();

[jsulm]

@LeeH said in Storing data from QnetworkReply:

QNetworkReply

You should connect your output() slot to http://doc.qt.io/qt-5/qiodevice.html#readyRead signal.

[LeeH]

@jsulm said in Storing data from QnetworkReply:

You should connect your output() slot to http://doc.qt.io/qt-5/qiodevice.html#readyRead signal.

Hi

Do you mean another connection, something like this:

void data::download(){

   _qnam->get(QNetworkRequest(QUrl("http://www.google.com")));
   QObject::connect(_qnam, SIGNAL(finished(QNetworkReply*)), this, SLOT(output(QNetworkReply*)));
   QObject::connect(QIODevice, SIGNAL(readyRead()), this, SLOT(output(QNetworkReply*)));

}

I know the QIODevice usage here is wrong, but just trying to get an idea

thanks

[jsulm]

@LeeH No need for two connections, the one for readyRead() is enough

[LeeH]

@jsulm

Ok... so how should I use QIOdevice here:

QObject::connect(QIODevice, SIGNAL(readyRead()), this, SLOT(output(QNetworkReply*)));

i get error: "expecting primary expression before ',' token" and it can't be instantiated

thanks

[m.sue]

Hi @LeeH

You need the QIODevice type object not the class name there.

-Michael.

[LeeH]

@m.sue

Hi,

QIODevice is an abstract class.

[m.sue]

Hi @LeeH

then the object of the derived class that you use.

-Michael.

[LeeH]

@m.sue said in Storing data from QnetworkReply:

then the object of the derived class that you use.

I modified my code to use readRead() from QNetworkReply object and it still doesn't work:

...
void data::download(){

_rep = _qnam->get(QNetworkRequest(QUrl("http://www.google.com")));
QObject::connect(_rep, SIGNAL(readyRead()), this, SLOT(output()));

}

void data::output(){

    if(!_rep->error()){

       _ba.append(_rep->readAll());

    }
    else{
        qDebug() << _rep->error();
    }
    _rep->deleteLater();
}

[m.sue]

Hi @LeeH

I would write: connect(_rep, SIGNAL(readyRead()), SLOT(output())); But this should not be essential.

So maybe output() is not a slot.

-Michael.

[mrjj]

@LeeH said in Storing data from QnetworkReply:

qDebug() << _rep->error();

Is line ever activated ?
is _ba.append called ?

[LeeH]

@m.sue said in Storing data from QnetworkReply:

So maybe output() is not a slot.

Hi it's always been a public slot... and i do get server reply data

[LeeH]

@mrjj said in Storing data from QnetworkReply:

Is line ever activated ?
is _ba.append called ?

Hi, there are no errors from server, and I always get reply.
I call _ba from main() using data::get()

[mrjj]

@LeeH
but is data appended?

if(!_rep->error()){
_ba.append(_rep->readAll());
qDebug() <<"size" << _ba.size();
}

have you tried with a breakpoint ?
is data::output() called?

[LeeH]

@mrjj

When I added:

qDebug() <<"size" << _ba.size();

i got:

size 2634

Yes data::output() is definately being called

[mrjj]

@LeeH
So what is not working ?
You clearly read data into _ba.

[LeeH]

@mrjj

but my data::get() I use to read _ba that i call from main() after downloading, is empty(""), where as if I read _ba from the slot inside the class I can see all my data

[LeeH]

@LeeH

You know I think It's best I just stick to saving to file, that seem's to be the only way I can be sure my data sticks around and can be used anywhere.... I thank everyone for their help, and apologize for wasting all of our time!

[ambershark]

@LeeH Well here's your problem:

QByteArray data::get(){
    qDebug() << _ba;
}

You don't return anything. You should have gotten at least a compiler warning from that.

Anyway, just edit to be:

QByteArray data::get(){
    qDebug() << _ba;
    return _ba;
}

And your data.get() will work.

There is no reason to save the data to a file. You're just wasting resources on disk and slowing your app down for no reason.