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c++qtqt5

Add dynamic variables to an url

I would like to add dynamic variables to an url example:

QNetworkRequest req( QUrl( QString("http://website.com/?test=1&id=1") ) );

But when i try this:

// the HTTP request
varUrl = "http://website.com/?test=";
varUrl += info;
varUrl += "&id=";
varUrl += info_2;

QNetworkRequest req( QUrl( QString(varUrl) ) );
QNetworkReply *reply = mgr.get(req);
eventLoop.exec(); // blocks stack until "finished()" has been called

i get this error:

enter image description here

Solution

  • The error message you posted is partly unrelated. Your actual problem is this:

    QNetworkRequest req( QUrl( QString(varUrl) ) );

    This is treated as a function declaration. This is a corner case in C++ and it's commonly referred to as the "most vexing parse". See https://en.wikipedia.org/wiki/Most_vexing_parse for an explanation.

    In any event, use the QUrl::fromUserInput() static function instead of passing the query string directly. This will encode the query correctly (otherwise you'd need to manually encode the query correctly by hand.) So in short, change the above line to:

    QNetworkRequest req(QUrl::fromUserInput(varUrl));

    This also fixes the parsing issue; the above is treated correctly like a variable definition, not a function declaration, and your code should now compile fine.

    As a side-note, you can use the QString::arg() function to construct your string in one go, without having to use append (+=) operations. So you can construct your URL string like this:

    varUrl = QString("http://website.com/?test=%1&id=%2").arg(info).arg(info_2);

    %1 will be replaced with the contents of info, and %2 with the contents of info_2.