qt5 connect to lambda

[Marek]

@hskoglund
Thanks for reply,
but with QSignalMapper I can't grab parameters from signal right? I can set some mappings, but what is being send from signal is lost.

[Marek]

@mrjj

Hi,

Of course! It works for me ;)
Thanks for the tip!

Marek

[VRonin]

you should use Qt5 connection sintax https://wiki.qt.io/New_Signal_Slot_Syntax.

connect(netReply,&QNetworkReply::downloadProgress,[=](qint64 bytesReceived, qint64 bytesTotal)->void{downloadProgress(bytesReceived,bytesTotal,netReply);});

or

connect(netReply,&QNetworkReply::downloadProgress,[&](qint64 bytesReceived, qint64 bytesTotal)->void{downloadProgress(bytesReceived,bytesTotal,my_int_value);});

[VRonin]

@mrjj While useful, isn't sender() a fast way to bad design?

[mrjj]

@VRonin
Well if overused it leads to ugly code with many casts.
So yes, one could say its not optimal. :)

And if possible lambdas, much better indeed.

[Marek]

@VRonin

It would be what I was asking for, but I have an error during compilation

download-mgr.cpp:29:44: error: invalid use of non-static member function 'void QNetworkReply::downloadProgress(qint64, qint64)'
         connect(d->netReply,QNetworkReply::downloadProgress,[=](qint64 bytesReceived, qint64 bytesTotal)->void{downloadProgress(bytesReceived,bytesTotal,d->netReply);});

My header:

void downloadProgress(qint64 recvBytes,qint64 totalFileBytes,QNetworkReply *netReply);

source:

void DownloadMgr::downloadProgress(qint64 recvBytes, qint64 totalFileBytes,QNetworkReply *netReply) {
    downloadMap[netReply]->recvBytes=recvBytes;
    this->calcPercentDownloaded();
}

connect:

connect(d->netReply,QNetworkReply::downloadProgress,[=](qint64 bytesReceived, qint64 bytesTotal)->void{downloadProgress(bytesReceived,bytesTotal,d->netReply);});

What can be wrong?

[VRonin]

sorry forgot an &

connect(d->netReply,&QNetworkReply::downloadProgress etcetera

I will correct the post above accordigly

[mrjj]

Just a note
if using older mingw
you might need
CONFIG+=C++11 ( in the .pro file)
to enable c++11 which this syntax needs.

[Marek]

Thanks all,

It works as it should,
Thanks a lot ;)
Very useful this new connect with lambda

Marek

[sonichy]

connect(reply, &QNetworkReply::downloadProgress, [=](qint64 bytesReceived, qint64 bytesTotal){
......
});