内容

• 公共函数
• 相关非成员
• 详细描述
• Basic Use
• Formatting Options
• Writing Custom Types to a Stream

QDebug Class

QDebug class provides an output stream for debugging information. 更多...

头：	#include <QDebug>
qmake:	QT += core

• 所有成员列表，包括继承成员

公共函数

	QDebug (QIODevice * device )
	QDebug (QString * string )
	QDebug (QtMsgType type )
	QDebug (const QDebug & other )
	~QDebug ()
bool	autoInsertSpaces () const
QDebug &	maybeQuote (char c = '"')
QDebug &	maybeSpace ()
QDebug &	noquote ()
QDebug &	nospace ()
QDebug &	quote ()
QDebug &	resetFormat ()
void	setAutoInsertSpaces (bool b )
void	setVerbosity (int verbosityLevel )
QDebug &	space ()
void	swap (QDebug & other )
int	verbosity () const
QDebug &	operator<< (QChar t )
QDebug &	operator<< (bool t )
QDebug &	operator<< (char t )
QDebug &	operator<< (signed short i )
QDebug &	operator<< (unsigned short i )
QDebug &	operator<< (char16_t t )
QDebug &	operator<< (char32_t t )
QDebug &	operator<< (signed int i )
QDebug &	operator<< (unsigned int i )
QDebug &	operator<< (signed long l )
QDebug &	operator<< (unsigned long l )
QDebug &	operator<< (qint64 i )
QDebug &	operator<< (quint64 i )
QDebug &	operator<< (float f )
QDebug &	operator<< (double f )
QDebug &	operator<< (const char * s )
QDebug &	operator<< (const QString & s )
QDebug &	operator<< (const QStringRef & s )
QDebug &	operator<< (QLatin1String s )
QDebug &	operator<< (const QByteArray & b )
QDebug &	operator<< (const void * p )
QDebug &	operator= (const QDebug & other )

相关非成员

QDebug	operator<< (QDebug stream , const QList<T> & list )
QDebug	operator<< (QDebug stream , const std::list<T, Alloc> & list )
QDebug	operator<< (QDebug stream , const QVector<T> & vector )
QDebug	operator<< (QDebug stream , const std::vector<T, Alloc> & vector )
QDebug	operator<< (QDebug stream , const QSet<T> & set )
QDebug	operator<< (QDebug stream , const QMap<Key, T> & map )
QDebug	operator<< (QDebug stream , const std::map<Key, T, Compare, Alloc> & map )
QDebug	operator<< (QDebug stream , const std::multimap<Key, T, Compare, Alloc> & map )
QDebug	operator<< (QDebug stream , const QHash<Key, T> & hash )
QDebug	operator<< (QDebug stream , const QPair<T1, T2> & pair )
QDebug	operator<< (QDebug stream , const QFlags<T> & flag )

详细描述

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 () 和 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.

Formatting Options

QDebug formats output so that it's easily readable. It automatically adds spaces between arguments, and adds quotes around QString , QByteArray , QChar 自变量。

You can tweak these options through the space (), nospace () 和 quote (), noquote () methods. Furthermore, QTextStream manipulators can be piped into a QDebug stream.

QDebugStateSaver limits changes to the formatting to the current scope. resetFormat () resets the options to the default ones.

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 debug, const Coordinate &c)
{
    QDebugStateSaver saver(debug);
    debug.nospace() << '(' << c.x() << ", " << c.y() << ')';
    return debug;
}
					

This is described in the 调试技术 and 创建自定义 Qt 类型 documents.

成员函数文档编制

QDebug:: QDebug ( QIODevice * device )

Constructs a debug stream that writes to the given device .

QDebug:: QDebug ( QString * string )

Constructs a debug stream that writes to the given string .

QDebug:: QDebug ( QtMsgType type )

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

QDebug:: QDebug (const QDebug & other )

构造副本为 other debug stream.

QDebug:: ~QDebug ()

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

bool QDebug:: autoInsertSpaces () const

返回 true 若此 QDebug instance will automatically insert spaces between writes.

该函数在 Qt 5.0 引入。

另请参阅 setAutoInsertSpaces () 和 QDebugStateSaver .

QDebug &QDebug:: maybeQuote ( char c = '"')

Writes a character c to the debug stream, depending on the current setting for automatic insertion of quotes, and returns a reference to the stream.

The default character is a double quote " .

该函数在 Qt 5.4 引入。

另请参阅 quote () 和 noquote ().

QDebug &QDebug:: maybeSpace ()

Writes a space character to the debug stream, depending on the current setting for automatic insertion of spaces, and returns a reference to the stream.

另请参阅 space () 和 nospace ().

QDebug &QDebug:: noquote ()

Disables automatic insertion of quotation characters around QChar , QString and QByteArray contents and returns a reference to the stream.

When quoting is disabled, these types are printed without quotation characters and without escaping of non-printable characters.

该函数在 Qt 5.4 引入。

另请参阅 quote () 和 maybeQuote ().

QDebug &QDebug:: nospace ()

Disables automatic insertion of spaces and returns a reference to the stream.

另请参阅 space () 和 maybeSpace ().

QDebug &QDebug:: quote ()

Enables automatic insertion of quotation characters around QChar , QString and QByteArray contents and returns a reference to the stream.

Quoting is enabled by default.

该函数在 Qt 5.4 引入。

另请参阅 noquote () 和 maybeQuote ().

QDebug &QDebug:: resetFormat ()

Resets the stream formatting options, bringing it back to its original constructed state.

该函数在 Qt 5.4 引入。

另请参阅 space () 和 quote ().

void QDebug:: setAutoInsertSpaces ( bool b )

Enables automatic insertion of spaces between writes if b is true; otherwise automatic insertion of spaces is disabled.

该函数在 Qt 5.0 引入。

另请参阅 autoInsertSpaces () 和 QDebugStateSaver .

void QDebug:: setVerbosity ( int verbosityLevel )

Sets the verbosity of the stream to verbosityLevel .

The allowed range is from 0 to 7. The default value is 2.

该函数在 Qt 5.6 引入。

另请参阅 verbosity ().

QDebug &QDebug:: space ()

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

The stream remembers that automatic insertion of spaces is enabled for future writes.

另请参阅 nospace () 和 maybeSpace ().

void QDebug:: swap ( QDebug & other )

Swaps this debug stream instance with other 。此函数非常快，且从不失败。

该函数在 Qt 5.0 引入。

int QDebug:: verbosity () const

Returns the verbosity of the debug stream.

Streaming operators can check the value to decide whether verbose output is desired and print more information depending on the level. Higher values indicate that more information is desired.

The allowed range is from 0 to 7. The default value is 2.

该函数在 Qt 5.6 引入。

另请参阅 setVerbosity ().

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

Writes the character, t , to the stream and returns a reference to the stream. Normally, QDebug prints control characters and non-US-ASCII characters as their C escape sequences or their Unicode value (\u1234). To print non-printable characters without transformation, enable the noquote () functionality, but note that some QDebug backends may not be 8-bit clean and may not be able to represent t .

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

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

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

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

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

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

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

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

QDebug &QDebug:: operator<< ( char16_t t )

Writes the UTF-16 character, t , to the stream and returns a reference to the stream.

该函数在 Qt 5.5 引入。

QDebug &QDebug:: operator<< ( char32_t t )

Writes the UTF-32 character, t , to the stream and returns a reference to the stream.

该函数在 Qt 5.5 引入。

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Writes the '\0'-terminated string, s , to the stream and returns a reference to the stream. The string is never quoted nor transformed to the output, but note that some QDebug backends might not be 8-bit clean.

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

Writes the string, s , to the stream and returns a reference to the stream. Normally, QDebug prints the string inside quotes and transforms non-printable characters to their Unicode values (\u1234).

To print non-printable characters without transformation, enable the noquote () functionality. Note that some QDebug backends might not be 8-bit clean.

Output examples:

QString s;
s = "a";
qDebug().noquote() << s;    // prints: a
qDebug() << s;              // prints: "a"
s = "\"a\r\n\"";
qDebug() << s;              // prints: "\"a\r\n\""
s = "\033";                 // escape character
qDebug() << s;              // prints: "\u001B"
s = "\u00AD";               // SOFT HYPHEN
qDebug() << s;              // prints: "\u00AD"
s = "\u00E1";               // LATIN SMALL LETTER A WITH ACUTE
qDebug() << s;              // prints: "á"
s = "a\u0301";              // "a" followed by COMBINING ACUTE ACCENT
qDebug() << s;              // prints: "á";
s = "\u0430\u0301";         // CYRILLIC SMALL LETTER A followed by COMBINING ACUTE ACCENT
qDebug() << s;              // prints: "а́"
					

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

Writes the string, s , to the stream and returns a reference to the stream. Normally, QDebug prints the string inside quotes and transforms non-printable characters to their Unicode values (\u1234).

To print non-printable characters without transformation, enable the noquote () functionality. Note that some QDebug backends might not be 8-bit clean.

见 QString overload for examples.

QDebug &QDebug:: operator<< ( QLatin1String s )

Writes the string, s , to the stream and returns a reference to the stream. Normally, QDebug prints the string inside quotes and transforms non-printable characters to their Unicode values (\u1234).

To print non-printable characters without transformation, enable the noquote () functionality. Note that some QDebug backends might not be 8-bit clean.

见 QString overload for examples.

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

Writes the byte array, b , to the stream and returns a reference to the stream. Normally, QDebug prints the array inside quotes and transforms control or non-US-ASCII characters to their C escape sequences (\xAB). This way, the output is always 7-bit clean and the string can be copied from the output and pasted back into C++ sources, if necessary.

To print non-printable characters without transformation, enable the noquote () functionality. Note that some QDebug backends might not be 8-bit clean.

Output examples:

QByteArray ba;
ba = "a";
qDebug().noquote() << ba;    // prints: a
qDebug() << ba;              // prints: "a"
ba = "\"a\r\n\"";
qDebug() << ba;              // prints: "\"a\r\n\""
ba = "\033";                 // escape character
qDebug() << ba;              // prints: "\x1B"
ba = "\xC3\xA1";
qDebug() << ba;              // prints: "\xC3\xA1"
ba = QByteArray("a\0b", 3);
qDebug() << ba               // prints: "\a\x00""b"
					

Note how QDebug needed to close and reopen the string in the way C and C++ languages concatenate string literals so that the letter 'b' is not interpreted as part of the previous hexadecimal escape sequence.

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

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

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

赋值 other debug stream to this stream and returns a reference to this stream.

相关非成员

QDebug operator<< ( QDebug stream , const QList < T > & list )

Writes the contents of list to stream . T needs to support streaming into QDebug .

QDebug operator<< ( QDebug stream , const std::list < T , Alloc > & list )

Writes the contents of list to stream . T needs to support streaming into QDebug .

该函数在 Qt 5.7 引入。

QDebug operator<< ( QDebug stream , const QVector < T > & vector )

Writes the contents of vector to stream . T needs to support streaming into QDebug .

QDebug operator<< ( QDebug stream , const std::vector < T , Alloc > & vector )

Writes the contents of vector to stream . T needs to support streaming into QDebug .

该函数在 Qt 5.7 引入。

QDebug operator<< ( QDebug stream , const QSet < T > & set )

Writes the contents of set to stream . T needs to support streaming into QDebug .

QDebug operator<< ( QDebug stream , const QMap < Key , T > & map )

Writes the contents of map to stream . Both Key and T need to support streaming into QDebug .

QDebug operator<< ( QDebug stream , const std::map < Key , T , 比较 , Alloc > & map )

Writes the contents of map to stream . Both Key and T need to support streaming into QDebug .

该函数在 Qt 5.7 引入。

QDebug operator<< ( QDebug stream , const std::multimap < Key , T , 比较 , Alloc > & map )

Writes the contents of map to stream . Both Key and T need to support streaming into QDebug .

该函数在 Qt 5.7 引入。

QDebug operator<< ( QDebug stream , const QHash < Key , T > & hash )

Writes the contents of hash to stream . Both Key and T need to support streaming into QDebug .

QDebug operator<< ( QDebug stream , const QPair < T1 , T2 > & pair )

Writes the contents of pair to stream . Both T1 and T2 need to support streaming into QDebug .

QDebug operator<< ( QDebug stream , const QFlags < T > & flag )

写入 flag to stream .

该函数在 Qt 4.7 引入。