QRegularExpressionValidator Class

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

Header: #include <QRegularExpressionValidator>
CMake: find_package(Qt6 REQUIRED COMPONENTS Gui)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: QT += gui
Inherits: QValidator


Public Functions

QRegularExpressionValidator(QObject *parent = nullptr)
QRegularExpressionValidator(const QRegularExpression &re, QObject *parent = nullptr)
virtual ~QRegularExpressionValidator()
QRegularExpression regularExpression() const

Reimplemented Public Functions

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

Public Slots

void setRegularExpression(const QRegularExpression &re)


void regularExpressionChanged(const QRegularExpression &re)

Detailed Description

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

If the regexp partially matches against the string, the result is considered Intermediate. For example, "" and "A" are Intermediate for the regexp [A-Z][0-9] (whereas "_" would be Invalid).

QRegularExpressionValidator automatically wraps the regular expression in the \\A and \\z anchors; in other words, it always attempts to do an exact match.

Example of use:

// regexp: optional '-' followed by between 1 and 3 digits
QRegularExpression rx("-?\\d{1,3}");
QValidator *validator = new QRegularExpressionValidator(rx, this);

QLineEdit *edit = new QLineEdit(this);

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
QRegularExpression re("[1-9]\\d{0,3}");
// the validator treats the regexp as "^[1-9]\\d{0,3}$"
QRegularExpressionValidator v(re, 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

re.setPattern("\\S+");            // one or more non-whitespace characters
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
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
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 QRegularExpression, QIntValidator, and QDoubleValidator.

Property Documentation

regularExpression : QRegularExpression

This property holds the regular expression used for validation

By default, this property contains a regular expression with an empty pattern (which therefore matches any string).

Access functions:

QRegularExpression regularExpression() const
void setRegularExpression(const QRegularExpression &re)

Notifier signal:

void regularExpressionChanged(const QRegularExpression &re)

Member Function Documentation

[explicit] QRegularExpressionValidator::QRegularExpressionValidator(QObject *parent = nullptr)

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

[explicit] QRegularExpressionValidator::QRegularExpressionValidator(const QRegularExpression &re, QObject *parent = nullptr)

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

[virtual noexcept] QRegularExpressionValidator::~QRegularExpressionValidator()

Destroys the validator.

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

Reimplements: QValidator::validate(QString &input, int &pos) const.

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.

In case the input is not matched, the pos parameter is set to the length of the input parameter; otherwise, it is not modified.

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 QRegularExpression::match().

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