Qt 5.11 | Qt GUI | C++ Classes | QRegExpValidator

Qt 5.11.3 Reference Documentation

# QRegExpValidator Class

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

Header: | #include <QRegExpValidator>
qmake: | QT += gui
Inherits: | QValidator

- List of all members, including inherited members

## Properties

- regExp : QRegExp

## Public Functions

| QRegExpValidator(QObject *parent = nullptr)
| QRegExpValidator(const QRegExp &rx, QObject *parent = nullptr)
virtual | ~QRegExpValidator()
const QRegExp & | regExp() const
void | setRegExp(const QRegExp &rx)

## Reimplemented Public Functions

virtual QValidator::State | validate(QString &input, int &pos) const override

- 4 public functions inherited from QValidator

### Additional Inherited Members

- 1 signal inherited from QValidator

## 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.

When QRegExpValidator determines whether a string is Acceptable or not, the regexp is treated as if it begins with the start of string assertion (^) and ends with the end of string assertion ($); the match is against the entire input string, or from the given position if a start position greater than zero is given.

If a string is a prefix of an Acceptable string, it is considered Intermediate. For example, "" and "A" are Intermediate for the regexp [A-Z][0-9] (whereas "_" would be Invalid).

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, QDoubleValidator, and Settings Editor Example.

## Property Documentation

### regExp : QRegExp

This property holds the regular expression used for validation

By default, this property contains a regular expression with the pattern `.*` that matches any string.

Access functions:

const QRegExp & | regExp() const
void | setRegExp(const QRegExp &rx)

## Member Function Documentation

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

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

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

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]+$.

### `[virtual]` QRegExpValidator::~QRegExpValidator()

Destroys the validator.

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

Reimplemented from QValidator::validate().

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.

Additionally, 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.

See also QRegExp::exactMatch().