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# QRegExpValidator Class Reference
[QtGui module]

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

    #include <QRegExpValidator>

Inherits QValidator.

- List of all members, including inherited members
- Qt 3 support members

### Public Functions

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

- 2 public functions inherited from QValidator
- 28 public functions inherited from QObject

### Additional Inherited Members

- 1 property inherited from QObject
- 1 public slot inherited from QObject
- 1 signal inherited from QObject
- 4 static public members inherited from QObject
- 7 protected functions inherited from QObject

## Detailed Description

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

QRegExpValidator uses a regular expression (regexp) to determine whether an input string is Acceptable, Intermediate, or Invalid. The regexp can either be supplied when the QRegExpValidator is constructed, or at a later time.

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}");
        QValidator *validator = new QRegExpValidator(rx, this);

        QLineEdit *edit = new QLineEdit(this);
        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;
        int pos = 0;

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

        rx.setPattern("\\S+");            // one or more non-whitespace characters
        v.setRegExp(rx);
        s = "myfile.txt";  v.validate(s, pos); // Returns Acceptable
        s = "my file.txt"; v.validate(s, pos); // 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, pos);        // Returns Invalid
        s = "A12345Z"; v.validate(s, pos);        // Returns Acceptable
        s = "B12";     v.validate(s, pos);        // 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, pos); // Returns Acceptable
        s = "README.1ST";  v.validate(s, pos); // Returns Acceptable
        s = "read me.txt"; v.validate(s, pos); // Returns Invalid
        s = "readm";       v.validate(s, pos); // Returns Intermediate

See also QRegExp, QIntValidator, and QDoubleValidator.

## Member Function Documentation

### QRegExpValidator::QRegExpValidator ( QObject * parent )

Constructs a validator with a parent object that accepts any string (including an empty one) as valid.

### QRegExpValidator::QRegExpValidator ( const QRegExp & rx, QObject * parent )

Constructs a validator with a parent object that accepts all strings that match the regular expression rx.

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.

### 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 pos parameter is set to the length of the input parameter.

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

Reimplemented from QValidator.

See also QRegExp::exactMatch().