Qtopia Home - Classes - Hierachy - Annotated - Functions - Licenses - Reference

QRegExp Class Reference

The QRegExp class provides pattern matching using regular expressions or wildcards. More...

#include <qregexp.h>

List of all member functions.

Public Members

QRegExp ()
QRegExp ( const QString & pattern, bool caseSensitive = TRUE, bool wildcard = FALSE )
QRegExp ( const QRegExp & r )
~QRegExp ()
QRegExp & operator= ( const QRegExp & r )
QRegExp & operator= ( const QString & pattern ) (obsolete)
bool operator== ( const QRegExp & r ) const
bool operator!= ( const QRegExp & r ) const
bool isEmpty () const
bool isValid () const
bool caseSensitive () const
void setCaseSensitive ( bool enable )
bool wildcard () const
void setWildcard ( bool wildcard )
QString pattern () const
void setPattern ( const QString & pattern )
int match ( const QString & str, int index = 0, int * len = 0, bool indexIsStart = TRUE ) const
int find ( const QString & str, int index )

Detailed Description

The QRegExp class provides pattern matching using regular expressions or wildcards.

QRegExp knows these regexp primitives:

c matches the character 'c'
. matches any character
^ matches start of input
$ matches end of input
[] matches a defined set of characters - see below.
a* matches a sequence of zero or more a's
a+ matches a sequence of one or more a's
a? matches an optional a
</dfn> escape code for matching special characters such as \, [, *, +, . etc.
\t matches the TAB character (9)
\n matches newline (10)
\r matches return (13)
\s matches a white space (defined as any character for which QChar::isSpace() returns TRUE. This includes at least ASCII characters 9 (TAB), 10 (LF), 11 (VT), 12(FF), 13 (CR) and 32 (Space)).
\d matches a digit (defined as any character for which QChar::isDigit() returns TRUE. This includes at least ASCII characters '0'-'9').
\x1f6b matches the character with unicode point U1f6b (hexadecimal 1f6b). \x0012 will match the ASCII/Latin1 character 0x12 (18 decimal, 12 hexadecimal).
\022 matches the ASCII/Latin1 character 022 (18 decimal, 22 octal).

In wildcard mode, it only knows four primitives:

c matches the character 'c'
? matches any character
* matches any sequence of characters
[] matches a defined set of characters - see below.

QRegExp supports Unicode both in the pattern strings and in the strings to be matched.

When writing regular expressions in C++ code, remember that C++ processes \ characters. So in order to match e.g. a "." character, you must write "\." in C++ source, not "\.".

A character set matches a defined set of characters. For example, [BSD] matches any of 'B', 'D' and 'S'. Within a character set, the special characters '.', '*', '?', '^', '$', '+' and '[' lose their special meanings. The following special characters apply:

^ When placed first in the list, changes the character set to match any character not in the list. To include the character '^' itself in the set, escape it or place it anywhere but first.
- Defines a range of characters. To include the character '-' itself in the set, escape it or place it last.
] Ends the character set definition. To include the character ']' itself in the set, escape it or place it first (but after the negation operator '^', if present)

Thus, [a-zA-Z0-9.] matches upper and lower case ASCII letters, digits and dot; and [^\s] matches everything except white space.

Bugs and limitations:

Case insensitive matching is not supported for non-ASCII/Latin1 (non-8bit) characters. Any character with a non-zero QChar.row() is matched case sensitively even if the QRegExp is in case insensitive mode.
Note: In Qt 3.0, the language of regular expressions will contain five more special characters, namely '(', ')', '{', '|' and '}'. To ease porting, it's a good idea to escape these characters with a backslash in all the regular expressions you'll write from now on.

Member Function Documentation

QRegExp::QRegExp ()

Constructs an empty regular expression.

QRegExp::QRegExp ( const QString & pattern, bool caseSensitive = TRUE, bool wildcard = FALSE )

Constructs a regular expression.

\arg pattern is the regular expression pattern string. \arg caseSensitive specifies whether or not to use case sensitive matching. \arg wildcard specifies whether the pattern string should be used for wildcard matching (also called globbing expression), normally used for matching file names.

QRegExp::QRegExp ( const QRegExp & r )

Constructs a regular expression which is a copy of r.

QRegExp::~QRegExp ()

Destructs the regular expression and cleans up its internal data.

bool QRegExp::caseSensitive () const

Returns TRUE if case sensitivity is enabled, otherwise FALSE. The default is TRUE.

int QRegExp::find ( const QString & str, int index )

Attempts to match in str, starting from position index. Returns the position of the match, or -1 if there was no match.

bool QRegExp::isEmpty () const

Returns TRUE if the regexp is empty.

bool QRegExp::isValid () const

Returns TRUE if the regexp is valid, or FALSE if it is invalid.

The pattern "[a-z" is an example of an invalid pattern, since it lacks a closing bracket.

int QRegExp::match ( const QString & str, int index = 0, int * len = 0, bool indexIsStart = TRUE ) const

Attempts to match in str, starting from position index. Returns the position of the match, or -1 if there was no match.

If len is not a null pointer, the length of the match is stored in *len.

If indexIsStart is TRUE (the default), the position index in the string will match the start-of-input primitive (^) in the regexp, if present. Otherwise, position 0 in str will match.

Example:

    QRegExp r("[0-9]*\\.[0-9]+");               // matches floating point
    int len;
    r.match("pi = 3.1416", 0, &len);            // returns 5, len == 6

Note: In Qt 3.0, this function will be replaced by find().

bool QRegExp::operator!= ( const QRegExp & r ) const

Returns TRUE if this regexp is not equal to r.

QRegExp & QRegExp::operator= ( const QRegExp & r )

Copies the regexp r and returns a reference to this regexp. The case sensitivity and wildcard options are copied, as well.

QRegExp & QRegExp::operator= ( const QString & pattern )

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

Consider using setPattern() instead of this method.

Sets the pattern string to pattern and returns a reference to this regexp. The case sensitivity or wildcard options do not change.

bool QRegExp::operator== ( const QRegExp & r ) const

Returns TRUE if this regexp is equal to r.

Two regexp objects are equal if they have equal pattern strings, case sensitivity options and wildcard options.

QString QRegExp::pattern () const

Returns the pattern string of the regexp.

void QRegExp::setCaseSensitive ( bool enable )

Enables or disables case sensitive matching.

In case sensitive mode, "a.e" matches "axe" but not "Axe".

void QRegExp::setPattern ( const QString & pattern )

Sets the pattern string to pattern and returns a reference to this regexp. The case sensitivity or wildcard options do not change.

void QRegExp::setWildcard ( bool wildcard )

Sets the wildcard option for the regular expression. The default is FALSE.

Setting wildcard to TRUE makes it convenient to match filenames instead of plain text.

For example, "qr*.cpp" matches the string "qregexp.cpp" in wildcard mode, but not "qicpp" (which would be matched in normal mode).

bool QRegExp::wildcard () const

Returns TRUE if wildcard mode is on, otherwise FALSE.