QRegularExpressionValidator Class

Detailed Description

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

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);
  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
  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
  v.setRegularExpression(re);
  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
  re.setPattern("[A-C]\\d{5}[W-Z]");
  v.setRegularExpression(re);
  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
  re.setPattern("read\\S?me(\.(txt|asc|1st))?");
  re.setPatternOptions(QRegularExpression::CaseInsensitiveOption);
  v.setRegularExpression(re);
  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