> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]
> On Behalf Of Igor Mironchik
> Sent: Friday, January 16, 2015 12:24 PM
> To: [email protected]
> Subject: [Interest] QTextStream doesn't write to QFile
>
> Hi. I'm doing a simple log class. I'm sure that Log creates after
> QCoreApplication.
> QCoreApplication is static. I create QCoreApplication as:
>
> static QSharedPointer< QCoreApplication > application(
> int argc = 0, char ** argv = 0 )
> {
> static QSharedPointer< QCoreApplication > app(
> new QCoreApplication( argc, argv ) );
>
> return app;
> }
It seems you're desperately trying here to extend QCoreApplications lifetime as
long as possible. This is just asking for trouble: just let QCoreApplication be
destructed when your application exits, in main.cpp.
> But this Log doesn't write anything to the file. File creates, I'm sure in
> it. But
> nothing writes. What is the reason?
Log is again declared as a static object, so the destructor runs when the app
is already unloading: This might be just too late to write stuff with QFile.
Instead, I'd use qAddPostRoutine or QCoreApplication::aboutToQuit() to close
the log file ... or just flush the file after every access: This involves of
course some overhead, but if your app crashes before exiting you have at least
some logging data :)
Regards
Kai
> And another problem is that QFile in destructor crashes application. Why?
>
> -------------------------------------------
> //! Severity
> enum Severity {
> //! Info.
> Info = 0,
> //! Warning.
> Warning = 1,
> //! Error.
> Error = 2,
> //! Critical.
> Critical = 3
> }; // enum Severity
>
> //
> // Log
> //
>
> class LogPrivate;
>
> //! Log.
> class Log {
> public:
> static Log & instance();
>
> Log & operator [] ( Severity s );
>
> Log & operator << ( const QString & data );
> Log & operator << ( const char * data );
>
> private:
> Log();
> ~Log();
>
> private:
> Q_DISABLE_COPY( Log )
>
> QScopedPointer< LogPrivate > d;
> }; // class Log
>
> #define LOG( S ) Log::instance()[ S ]
> -------------------------------------------
>
> And here is implementation:
>
> -------------------------------------------
> //
> // LogPrivate
> //
>
> class LogPrivate {
> public:
> LogPrivate()
> : severity( Info )
> {
> stream.setCodec( QTextCodec::codecForName( "UTF-8" ) );
> }
>
> ~LogPrivate()
> {
> stream.flush();
>
> if( file.isOpen() ) // HERE APPLICATION CRASHES !!!
> file.close(); }
>
> void initLogFile( const QDate & d )
> {
> if( date != d )
> {
> stream.flush();
>
> if( file.isOpen() )
> file.close();
>
> file.setFileName( QLatin1String( "./log/test." ) +
> d.toString( QLatin1String( "yy.MM.dd" ) ) +
> QLatin1String( ".log" ) );
> file.open( QIODevice::WriteOnly |
> QIODevice::Append );
>
> stream.setDevice( &file );
>
> date = d;
> }
> }
>
> QString severityToString() const
> {
> switch( severity )
> {
> case Info :
> return QLatin1String( "info" );
>
> case Warning :
> return QLatin1String( "warning" );
>
> case Error :
> return QLatin1String( "error" );
>
> case Critical :
> return QLatin1String( "critical" );
>
> default :
> return QString();
> }
> }
>
> //! Severity.
> Severity severity;
> //! Stream.
> QTextStream stream;
> //! File.
> QFile file;
> //! Date.
> QDate date;
> }; // class LogPrivate
>
>
> //
> // Log
> //
>
> Log &
> Log::instance()
> {
> static Log log;
>
> return log;
> }
>
> Log &
> Log::operator [] ( Severity s )
> {
> d->severity = s;
>
> d->initLogFile( QDate::currentDate() );
>
> d->stream << "\n" << "[" << QTime::currentTime().toString(
> QLatin1String( "hh:mm:ss" ) )
> << "] [" << d->severityToString() << "] ";
>
> d->severity = Info;
>
> return *this;
> }
>
> Log &
> Log::operator << ( const QString & data ) {
> d->stream << data;
>
> return *this;
> }
>
> Log &
> Log::operator << ( const char * data )
> {
> Log::operator << ( QString( data ) );
>
> return *this;
> }
>
> Log::Log()
> : d( new LogPrivate )
> {
> }
>
> Log::~Log()
> {
> }
> -------------------------------------------
>
>
> --
> Best Regards,
> Igor Mironchik.
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