QDebug Class Reference

The QDebug class provides an output stream for debugging information. More...

#include <qdebug.h>

Inheritance diagram for QDebug:

Classes
struct	Stream

Public Functions
QDebug &	maybeSpace ()
	Writes a space character to the debug stream, depending on the last character sent to the stream, and returns a reference to the stream. More...
QDebug &	nospace ()
	Clears the stream's internal flag that records whether the last character was a space and returns a reference to the stream. More...
QDebug &	operator<< (QChar t)
	Writes the character, t, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (QBool t)
	Writes the boolean value, t, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (bool t)
	Writes the boolean value, t, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (char t)
	Writes the character, t, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (signed short t)
	Writes the signed short integer, i, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (unsigned short t)
	Writes then unsigned short integer, i, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (signed int t)
	Writes the signed integer, i, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (unsigned int t)
	Writes then unsigned integer, i, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (signed long t)
	Writes the signed long integer, l, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (unsigned long t)
	Writes then unsigned long integer, l, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (qint64 t)
	Writes the signed 64-bit integer, i, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (quint64 t)
	Writes then unsigned 64-bit integer, i, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (float t)
	Writes the 32-bit floating point number, f, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (double t)
	Writes the 64-bit floating point number, f, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (const char *t)
	Writes the '\0'-terminated string, s, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (const QString &t)
	Writes the string, s, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (const QStringRef &t)
	Writes the string reference, s, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (const QLatin1String &t)
	Writes the Latin1-encoded string, s, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (const QByteArray &t)
	Writes the byte array, b, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (const void *t)
	Writes a pointer, p, to the stream and returns a reference to the stream. More...
QDebug &	operator<< (QTextStreamFunction f)
QDebug &	operator<< (QTextStreamManipulator m)
QDebug &	operator= (const QDebug &other)
	Assigns the other debug stream to this stream and returns a reference to this stream. More...
	QDebug (QIODevice *device)
	Constructs a debug stream that writes to the given device. More...
	QDebug (QString *string)
	Constructs a debug stream that writes to the given string. More...
	QDebug (QtMsgType t)
	Constructs a debug stream that writes to the handler for the message type specified by type. More...
	QDebug (const QDebug &o)
	Constructs a copy of the other debug stream. More...
QDebug &	space ()
	Writes a space character to the debug stream and returns a reference to the stream. More...
	~QDebug ()
	Flushes any pending data to be written and destroys the debug stream. More...

Properties
struct QDebug::Stream *	stream

Detailed Description

The QDebug class provides an output stream for debugging information.

QDebug is used whenever the developer needs to write out debugging or tracing information to a device, file, string or console.

Basic Use

In the common case, it is useful to call the qDebug() function to obtain a default QDebug object to use for writing debugging information.

    qDebug() << "Date:" << QDate::currentDate();
    qDebug() << "Types:" << QString("String") << QChar('x') << QRect(0, 10, 50, 40);
    qDebug() << "Custom coordinate type:" << coordinate;

This constructs a QDebug object using the constructor that accepts a QtMsgType value of QtDebugMsg. Similarly, the qWarning(), qCritical() and qFatal() functions also return QDebug objects for the corresponding message types.

The class also provides several constructors for other situations, including a constructor that accepts a QFile or any other QIODevice subclass that is used to write debugging information to files and other devices. The constructor that accepts a QString is used to write to a string for display or serialization.

Writing Custom Types to a Stream

Many standard types can be written to QDebug objects, and Qt provides support for most Qt value types. To add support for custom types, you need to implement a streaming operator, as in the following example:

QDebug operator<<(QDebug dbg, const Coordinate &c)
{
    dbg.nospace() << "(" << c.x() << ", " << c.y() << ")";
    
    return dbg.space();
}

This is described in the Debugging Techniques and Creating Custom Qt Types::Making the Type Printable{Creating Custom Qt Types} documents.

Definition at line 62 of file qdebug.h.

Constructors and Destructors

QDebug() [1/4]

QDebug::QDebug ( QIODevice *  device )

inline

Constructs a debug stream that writes to the given device.

Definition at line 76 of file qdebug.h.

: stream(new Stream(device)) {}

QDebug() [2/4]

QDebug::QDebug ( QString *  string )

inline

Constructs a debug stream that writes to the given string.

Definition at line 77 of file qdebug.h.

: stream(new Stream(string)) {}

QDebug() [3/4]

QDebug::QDebug ( QtMsgType  t )

inline

Constructs a debug stream that writes to the handler for the message type specified by type.

Definition at line 78 of file qdebug.h.

: stream(new Stream(t)) {}

QDebug() [4/4]

QDebug::QDebug ( const QDebug &  o )

inline

Constructs a copy of the other debug stream.

Definition at line 79 of file qdebug.h.

:stream(o.stream) { ++stream->ref; }

~QDebug()

QDebug::~QDebug ( )

inline

Flushes any pending data to be written and destroys the debug stream.

Definition at line 81 of file qdebug.h.

                     {
        if (!--stream->ref) {
            if(stream->message_output) {
                QT_TRY {
                    qt_message_output(stream->type, stream->buffer.toLocal8Bit().data());
                } QT_CATCH(std::bad_alloc&) { /* We're out of memory - give up. */ }
            }
            delete stream;
        }
    }

Functions

maybeSpace()

QDebug & QDebug::maybeSpace ( )

inline

Writes a space character to the debug stream, depending on the last character sent to the stream, and returns a reference to the stream.

If the last character was a space character, this function writes a space character to the stream; otherwise, no characters are written to the stream.

See also

space(), nospace()

Definition at line 93 of file qdebug.h.

Referenced by operator<<().

{ if (stream->space) stream->ts << ' '; return *this; }

nospace()

QDebug & QDebug::nospace ( )

inline

Clears the stream's internal flag that records whether the last character was a space and returns a reference to the stream.

See also

space(), maybeSpace()

Definition at line 92 of file qdebug.h.

Referenced by debugVariantList(), flagsDebug(), operator<<(), QDeclarativeInfo::QDeclarativeInfo(), and streamDebug().

{ stream->space = false; return *this; }

operator<<() [1/22]

QDebug & QDebug::operator<< ( QChar  t )

inline

Writes the character, t, to the stream and returns a reference to the stream.

Definition at line 95 of file qdebug.h.

Referenced by QDeclarativeInfo::operator<<().

{ stream->ts << '\'' << t << '\''; return maybeSpace(); }

operator<<() [2/22]

QDebug & QDebug::operator<< ( QBool  t )

inline

Writes the boolean value, t, to the stream and returns a reference to the stream.

Warning

This function is not part of the public interface.

Definition at line 96 of file qdebug.h.

{ stream->ts << (bool(t != 0) ? "true" : "false"); return maybeSpace(); }

operator<<() [3/22]

QDebug & QDebug::operator<< ( bool  t )

inline

Writes the boolean value, t, to the stream and returns a reference to the stream.

Definition at line 97 of file qdebug.h.

{ stream->ts << (t ? "true" : "false"); return maybeSpace(); }

operator<<() [4/22]

QDebug & QDebug::operator<< ( char  t )

inline

Writes the character, t, to the stream and returns a reference to the stream.

Definition at line 98 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [5/22]

QDebug & QDebug::operator<< ( signed short  t )

inline

Writes the signed short integer, i, to the stream and returns a reference to the stream.

Definition at line 99 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [6/22]

QDebug & QDebug::operator<< ( unsigned short  t )

inline

Writes then unsigned short integer, i, to the stream and returns a reference to the stream.

Definition at line 100 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [7/22]

QDebug & QDebug::operator<< ( signed int  t )

inline

Writes the signed integer, i, to the stream and returns a reference to the stream.

Definition at line 101 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [8/22]

QDebug & QDebug::operator<< ( unsigned int  t )

inline

Writes then unsigned integer, i, to the stream and returns a reference to the stream.

Definition at line 102 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [9/22]

QDebug & QDebug::operator<< ( signed long  t )

inline

Writes the signed long integer, l, to the stream and returns a reference to the stream.

Definition at line 103 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [10/22]

QDebug & QDebug::operator<< ( unsigned long  t )

inline

Writes then unsigned long integer, l, to the stream and returns a reference to the stream.

Definition at line 104 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [11/22]

QDebug & QDebug::operator<< ( qint64  t )

inline

Writes the signed 64-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 105 of file qdebug.h.

        { stream->ts << QString::number(t); return maybeSpace(); }

operator<<() [12/22]

QDebug & QDebug::operator<< ( quint64  t )

inline

Writes then unsigned 64-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 107 of file qdebug.h.

        { stream->ts << QString::number(t); return maybeSpace(); }

operator<<() [13/22]

QDebug & QDebug::operator<< ( float  t )

inline

Writes the 32-bit floating point number, f, to the stream and returns a reference to the stream.

Definition at line 109 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [14/22]

QDebug & QDebug::operator<< ( double  t )

inline

Writes the 64-bit floating point number, f, to the stream and returns a reference to the stream.

Definition at line 110 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [15/22]

QDebug & QDebug::operator<< ( const char *  t )

inline

Writes the '\0'-terminated string, s, to the stream and returns a reference to the stream.

Definition at line 111 of file qdebug.h.

{ stream->ts << QString::fromAscii(t); return maybeSpace(); }

operator<<() [16/22]

QDebug & QDebug::operator<< ( const QString &  t )

inline

Writes the string, s, to the stream and returns a reference to the stream.

Definition at line 112 of file qdebug.h.

{ stream->ts << '\"' << t  << '\"'; return maybeSpace(); }

operator<<() [17/22]

QDebug & QDebug::operator<< ( const QStringRef &  t )

inline

Writes the string reference, s, to the stream and returns a reference to the stream.

Definition at line 113 of file qdebug.h.

Referenced by operator<<().

{ return operator<<(t.toString()); }

operator<<() [18/22]

QDebug & QDebug::operator<< ( const QLatin1String &  t )

inline

Writes the Latin1-encoded string, s, to the stream and returns a reference to the stream.

Definition at line 114 of file qdebug.h.

{ stream->ts << '\"'  << t.latin1() << '\"'; return maybeSpace(); }

operator<<() [19/22]

QDebug & QDebug::operator<< ( const QByteArray &  t )

inline

Writes the byte array, b, to the stream and returns a reference to the stream.

Definition at line 115 of file qdebug.h.

{ stream->ts  << '\"' << t << '\"'; return maybeSpace(); }

operator<<() [20/22]

QDebug & QDebug::operator<< ( const void *  t )

inline

Writes a pointer, p, to the stream and returns a reference to the stream.

Definition at line 116 of file qdebug.h.

{ stream->ts << t; return maybeSpace(); }

operator<<() [21/22]

QDebug & QDebug::operator<< ( QTextStreamFunction  f )

inline

Warning

This function is not part of the public interface.

Definition at line 117 of file qdebug.h.

                                                     {
        stream->ts << f;
        return *this;
    }

operator<<() [22/22]

QDebug & QDebug::operator<< ( QTextStreamManipulator  m )

inline

Warning

This function is not part of the public interface.

Definition at line 122 of file qdebug.h.

    { stream->ts << m; return *this; }

operator=()

QDebug & QDebug::operator= ( const QDebug &  other )

inline

Assigns the other debug stream to this stream and returns a reference to this stream.

Definition at line 146 of file qdebug.h.

{
    if (this != &other) {
        QDebug copy(other);
        qSwap(stream, copy.stream);
    }
    return *this;
}

space()

QDebug & QDebug::space ( )

inline

Writes a space character to the debug stream and returns a reference to the stream.

The stream will record that the last character sent to the stream was a space.

See also

nospace(), maybeSpace()

Definition at line 91 of file qdebug.h.

Referenced by operator<<().

{ stream->space = true; stream->ts << ' '; return *this; }

Properties

stream

struct QDebug::Stream * QDebug::stream

private

Referenced by operator=().

---

The documentation for this class was generated from the following files:

• /src/corelib/io/qdebug.h
• /src/corelib/io/qdebug.cpp