Re-using QNetworkRequest in finished() slot issue

  • EDIT: Ok I figured out what was happening. My original request is a POST request using QHttp* classes. This automatically adds the Content-Type, Content-Length, MIME-Version headers afterwards. So when I copy the original request and try to use a get() request with these headers that are not supposed to be present for GETs, Qt doesn't know what to do. So now my actual question is, how can I remove headers from a QNetworkRequest object?

    Ok I'm officially lost on why this is not working. I have a QNAM handling my requests and using the QNAM finished() slot. Within this slot I am handling redirects by doing the following in PyQt:

    EDIT: I tried saving the original request as self.request and then using it as 'new_request = QNetworkRequest(self.request)' This works! But why can't I use reply.request()?!

    def slotFinished(self, reply):
        // If being redirected... 
        new_request = QNetworkRequest(reply.request()) // I want a copy of the original request with all it's set custom headers, etc.
        new_request.setUrl('')  // The only thing I change is the new URL we're being redirected to.
        new_request2 = QNetworkRequest(QUrl('')) // Why does this work, and not the above?
        self.manager.get(new_request)  // This does not do anything 
        self.manager.get(new_request2) // Works no problem

    I'm clueless to why this is happening...

    Any help would be appreciated

  • @Wallboy said in Re-using QNetworkRequest in finished() slot issue:

    So now my actual question is, how can I remove headers from a QNetworkRequest object?

    While it doesn't appear to be documented (so use at your own risk), QNetworkRequest::setHeader
    and QNetworkRequest::setRawHeader() both unset headers if the supplied value is NULL.

    You can see this in the Qt code here (for setHeader), and here and here (for setRawHeader).

    So you could do:

    new_request.setHeader(QNetworkRequest::ContentTypeHeader, QVariant());
    new_request.setHeader(QNetworkRequest::ContentLengthHeader, QVariant());
    new_request.setRawHeader("MIME-Version", QByteArray());

    Depending on your use case, you might be better off defining an explicit "white list" of safe headers you want to keep, such as:

    QList<QByteArray> whitelist;
    foreach (const QByteArray &headerName, new_request.rawHeaderList()) {
        if (!whitelist.contains(headerName)) {
            new_request.setRawHeader(headerName, QByteArray());

    Or you could copy, instead of delete, the whitelisted headers like:

    foreach (const QByteArray &headerName, original_request.rawHeaderList()) {
        if (whitelist.contains(headerName)) {
            new_request.setRawHeader(headerName, original_request.rawHeader(headerName));


  • Thanks! Using an empty QByteArray() works perfect for removing headers.

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