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Qt-interest Archive, May 2008
QEventLoop error.

Message 1 in thread

Hi.

  I have to make a library for download files from a url. The function what I use from download the files is the next:

void HttpGet::download(const QUrl &url, const QString &filename) {
    QFile file;
    QHttp http;
    QEventLoop loop;

    QObject::connect(&http, SIGNAL(done(bool)), &loop, SLOT(quit()));

    file.setFileName(filename);
    file.open(QIODevice::WriteOnly);

    http.setHost(url.host(), url.port(80));
    http.get(url.toEncoded(QUrl::RemoveScheme | QUrl::RemoveAuthority), &file);

    loop.exec();
}

but, when I call to the function, appears the next error:

"QEventLoop: Cannot be used without QApplication"

I need a library, not an application. Can someone help me?

Thanks in advance.

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Message 2 in thread
































Joan Carles Jimenez wrote:
> Hi.
> 
> I have to make a library for download files from a url. The function 
> what I use from download the files is the next:
> 
> void HttpGet::download(const QUrl &url, const QString &filename) {
> 
> QFile file;
> 
> QHttp http;
> 
> QEventLoop loop;
> 
> QObject::connect(&http, SIGNAL(done(bool)), &loop, SLOT(quit()));
> 
> file.setFileName(filename);
> 
> file.open(QIODevice::WriteOnly);
> 
> http.setHost(url.host(), url.port(80));
> 
> http.get(url.toEncoded(QUrl::RemoveScheme | QUrl::RemoveAuthority), &file);
> 
> loop.exec();
> 
> }
> 
> but, when I call to the function, appears the next error:
> 
> "QEventLoop: Cannot be used without QApplication"
> 
> I need a library, not an application. Can someone help me?
> 
> Thanks in advance.
> 
> -- 
> 
> Joan Carles Jimenez
> 
> jjcarles@xxxxxxxx
> 
I suppose you need to make HttpGet::download(const QUrl &url, const 
QString &filename, QEventLoop& loop)
and pass the event loop with every call. QEventLoop is highly connected 
to QApplication as it handles all events for QApplication. Despite of 
the first impression, it is not asynchronous, but entering loop.exec() 
in your code is synchronous, so every event of the application can be 
treated inside the event loop, not only the QHttp events.

I'm not sure I explained it clearly? What I mean is: you cannot have 
QEventLoop without application.

Best regards,
Pawel Jaworski

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Message 3 in thread

































On Friday 30 May 2008 15:56:24 Pawel Jaworski wrote:
> I suppose you need to make HttpGet::download(const QUrl &url, const
> QString &filename, QEventLoop& loop)
> and pass the event loop with every call. QEventLoop is highly connected
> to QApplication as it handles all events for QApplication. Despite of
> the first impression, it is not asynchronous, but entering loop.exec()
> in your code is synchronous, so every event of the application can be
> treated inside the event loop, not only the QHttp events.
>

Yes, the code is synchronous. This function is for download a data file. After 
download, another function (in the same library) plot the values using QWT.

> I'm not sure I explained it clearly? What I mean is: you cannot have
> QEventLoop without application.
>

Then, I have a problem. My objective is create a library for extend Python and 
to call it  with "import" command. And I not have a QApplication.

Does any solution?

Cheers!

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