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# QRegExpValidator Class Reference

The QRegExpValidator class is used to check a string against a regular expression. More...

`#include <qvalidator.h>`

Inherits QValidator.

List of all member functions.

## Public Members

- QRegExpValidator ( QObject * parent, const char * name = 0 )
- QRegExpValidator ( const QRegExp & rx, QObject * parent, const char * name = 0 )
- ~QRegExpValidator ()
- virtual QValidator::State validate ( QString & input, int & pos ) const
- void setRegExp ( const QRegExp & rx )
- const QRegExp & regExp () const

## Detailed Description

The QRegExpValidator class is used to check a string against a regular expression.

QRegExpValidator contains a regular expression, "regexp", used to determine whether an input string is Acceptable, Intermediate or Invalid.

The regexp is treated as if it begins with the start of string assertion, `^`, and ends with the end of string assertion `$` so the match is against the entire input string, or from the given position if a start position greater than zero is given.

For a brief introduction to Qt's regexp engine see QRegExp.

Example of use:

        // regexp: optional '-' followed by between 1 and 3 digits
        QRegExp rx( "-?\\d{1,3}" );
        QRegExpValidator validator( rx, 0 );

        QLineEdit *edit = new QLineEdit( split );
        edit->setValidator( &validator );

Below we present some examples of validators. In practice they would normally be associated with a widget as in the example above.

        // integers 1 to 9999
        QRegExp rx( "[1-9]\\d{0,3}" );
        // the validator treats the regexp as "^[1-9]\\d{0,3}$"
        QRegExpValidator v( rx, 0 );
        QString s;

        s = "0";     v.validate( s, 0 );    // returns Invalid
        s = "12345"; v.validate( s, 0 );    // returns Invalid
        s = "1";     v.validate( s, 0 );    // returns Acceptable

        rx.setPattern( "\\S+" );            // one or more non-whitespace characters
        v.setRegExp( rx );
        s = "myfile.txt";  v.validate( s, 0 ); // Returns Acceptable
        s = "my file.txt"; v.validate( s, 0 ); // Returns Invalid

        // A, B or C followed by exactly five digits followed by W, X, Y or Z
        rx.setPattern( "[A-C]\\d{5}[W-Z]" );
        v.setRegExp( rx );
        s = "a12345Z"; v.validate( s, 0 );  // Returns Invalid
        s = "A12345Z"; v.validate( s, 0 );  // Returns Acceptable
        s = "B12";     v.validate( s, 0 );  // Returns Intermediate

        // match most 'readme' files
        rx.setPattern( "read\\S?me(\.(txt|asc|1st))?" );
        rx.setCaseSensitive( FALSE );
        v.setRegExp( rx );
        s = "readme";      v.validate( s, 0 ); // Returns Acceptable
        s = "README.1ST";  v.validate( s, 0 ); // Returns Acceptable
        s = "read me.txt"; v.validate( s, 0 ); // Returns Invalid
        s = "readm";       v.validate( s, 0 ); // Returns Intermediate

See also QRegExp, QIntValidator, QDoubleValidator and Miscellaneous Classes.

## Member Function Documentation

### QRegExpValidator::QRegExpValidator ( QObject * parent, const char * name = 0 )

Constructs a validator that accepts any string (including an empty one) as valid. The object's parent is parent and its name is name.

### QRegExpValidator::QRegExpValidator ( const QRegExp & rx, QObject * parent, const char * name = 0 )

Constructs a validator which accepts all strings that match the regular expression rx. The object's parent is parent and its name is name.

The match is made against the entire string, e.g. if the regexp is [A-Fa-f0-9]+ it will be treated as ^[A-Fa-f0-9]+$.

### QRegExpValidator::~QRegExpValidator ()

Destroys the validator, freeing any resources allocated.

### const QRegExp & QRegExpValidator::regExp () const

Returns the regular expression used for validation.

See also setRegExp().

### void QRegExpValidator::setRegExp ( const QRegExp & rx )

Sets the regular expression used for validation to rx.

See also regExp().

### QValidator::State QRegExpValidator::validate ( QString & input, int & pos ) const`[virtual]`

Returns Acceptable if input is matched by the regular expression for this validator, Intermediate if it has matched partially (i.e. could be a valid match if additional valid characters are added), and Invalid if input is not matched.

The start position is the beginning of the string unless pos is given and is > 0 in which case the regexp is matched from pos until the end of the string.

For example, if the regular expression is \w\d\d (that is, word-character, digit, digit) then "A57" is Acceptable, "E5" is Intermediate and "+9" is Invalid.

See also QRegExp::match().

Reimplemented from QValidator.

This file is part of the Qt toolkit, copyright © 1995-2001 Trolltech, all rights reserved.