QValidator

NAME

SYNOPSIS

Inherits QObject.

Inherited by QIntValidator, QDoubleValidator, and QRegExpValidator.

Public Members

DESCRIPTION

The class itself is abstract. Two subclasses, QIntValidator and QDoubleValidator, provide basic numeric-range checking, and QRegExpValidator provides general checking using a custom regular expression.

If the built-in validators aren't sufficient, you can subclass QValidator. The class has two virtual functions: validate() and fixup().

validate() must be implemented by every subclass. It returns Invalid, Intermediate or Acceptable depending on whether its argument is valid (for the subclass's definition of valid).

These three states require some explanation. An Invalid string is clearly invalid. Intermediate is less obvious: the concept of validity is slippery when the string is incomplete (still being edited). QValidator defines Intermediate as the property of a string that is neither clearly invalid nor acceptable as a final result. Acceptable means that the string is acceptable as a final result. One might say that any string that is a plausible intermediate state during entry of an Acceptable string is Intermediate.

Here are some examples:

For a line edit that accepts integers from 0 to 999 inclusive, 42 and 123 are Acceptable, the empty string and 1114 are Intermediate and asdf is Invalid.

For an editable combobox that accepts URLs, any well-formed URL is Acceptable, "http://www.trolltech.com/," is Intermediate (it might be a cut and paste operation that accidentally took in a comma at the end), the empty string is Intermediate (the user might select and delete all of the text in preparation for entering a new URL), and "http:///./" is Invalid.

For a spin box that accepts lengths, "11cm" and "1in" are Acceptable, "11" and the empty string are Intermediate and" http://www.trolltech.com" and "hour" are Invalid.

fixup() is provided for validators that can repair some user errors. The default implementation does nothing. QLineEdit, for example, will call fixup() if the user presses Enter (or Return) and the content is not currently valid. This allows the fixup() function the opportunity of performing some magic to make an Invalid string Acceptable.

QValidator is typically used with QLineEdit, QSpinBox and QComboBox.

See also Miscellaneous Classes.  

Member Type Documentation

QValidator::State

QValidator::Invalid - the string is clearly invalid.

QValidator::Intermediate - the string is a plausible intermediate value during editing.

QValidator::Acceptable - the string is acceptable as a final result, i.e. it is valid.

MEMBER FUNCTION DOCUMENTATION

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

QValidator::~QValidator ()

void QValidator::fixup ( QString & input ) const [virtual]

Reimplementations of this function can change input even if they do not produce a valid string. For example, an ISBN validator might want to delete every character except digits and "-", even if the result is still not a valid ISBN; a surname validator might want to remove whitespace from the start and end of the string, even if the resulting string is not in the list of accepted surnames.  

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

The function can change input and pos (the cursor position) if it wants to.

Reimplemented in QIntValidator, QDoubleValidator, and QRegExpValidator.

SEE ALSO

COPYRIGHT

AUTHOR

BUGS