How to use QEventLoop?

[MorrisLiang]

The app I'm creating is relative to the network.I want it to check if the username/password is valid when it starts.And while validating,nothing can the user do.I also want to make the UI responsible.So I think of QEventLoop(I guess that's what I need,right?)

Here,I use validate() to check the info.

bool MyApp::validate()
{
    QString requestURL = "http://xxxxxx.com/check?username=aaa&password=bbb";
    QNetworkReply* reply= manager.get(QNetworkRequest(requestURL));
    ....
}

bool MyApp::validate()
{
    QString requestURL = "http://xxxxxx.com/check?username=aaa&password=bbb";
    QNetworkReply* reply= manager.get(QNetworkRequest(requestURL));
    ....
}

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HOW do I use QEventLoop inside the validate(),so that I can return ture/false,when the server tells me whether the info is correct.