QValidator(3qt)QValidator(3qt)NAMEQValidator - Validation of input text
#include <qvalidator.h>
Inherits QObject.
Inherited by QDoubleValidator and QIntValidator.
Public Members
QValidator ( QWidget * parent, const char * name = 0 )
~QValidator ()
enum State { Invalid, Intermediate, Valid=Intermediate,
Acceptable }
virtual State validate ( QString &, int & ) const
virtual void fixup ( QString & ) const
DESCRIPTION
The QValidator class provides validation of input text.
The class itself is abstract; two subclasses provide
rudimentary numeric range checking.
The class includes two virtual functions, validate() and
fixup().
validate() is pure virtual, so it must be implemented by
every subclass. It returns Invalid, Intermediate or
Acceptable depending on whether its argument is valid (for
the class' definition of valid).
The 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 it is
neither clearly invalid or 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:
1 For a line edit that accepts integers from 0 to 999
inclusive, 42 and 666 are Acceptable, the empty
string and 1114 are Intermediate and asdf is
Invalid.
2 For an editable combo box that accepts URLs, any
well-formed URL is Acceptable,
"http://www.trolltech.com/," is Intermediate (it
can be a cut-and-paste job that accidentally took
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in a comma at the end), the empty string is valid
(the user might select and delete all of the text
in preparation to entering a new URL), and"
http:///./" is Invalid.
3 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 or
all user errors. The default does nothing. QLineEdit, for
example, will call fixup() if the user presses Return and
the content is not currently valid, in case fixup() can do
magic. This allows some Invalid strings to be made
Acceptable, too, spoiling the muddy definition above even
more.
QValidator is generally used with QLineEdit, QSpinBox and
QComboBox.
Member Type Documentation
QValidator::State
This enum type defines the states in which a validated
string can be. There are currently three states:
Invalid - the string is clearly invalid.
Intermediate - the string is a plausible intermediate
value during editing.
Acceptable - acceptable as a final result.
The state Valid has been renamed Intermediate. The old
name confused too many people and is now obsolete.
MEMBER FUNCTION DOCUMENTATIONQValidator::QValidator ( QWidget * parent, const char * name = 0
)
Sets up the internal data structures used by the
validator. At the moment there aren't any.
QValidator::~QValidator ()
Destroys the validator, freeing any storage and other
resources used.
void QValidator::fixup ( QString & input ) const [virtual]
Attempts to change input to be valid according to this
validator's rules. Need not result in a valid string -
callers of this function must re-test afterwards. The
default does nothing.
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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 not a valid ISBN,
and a last-name validator might want to remove white space
from the start and end of the string, even if the
resulting string is not in the list of known last names.
QValidator::State QValidator::validate( QString & input, int &
pos ) const
This pure virtual function returns Invalid if input is
invalid according to this validator's rules, Intermediate
if it is likely that a little more editing will make the
input acceptable (e.g. the user types '4' into a widget
which accepts 10-99) and Acceptable if the input is
completely acceptable.
The function can change input and pos (the cursor
position) if it wants to.
SEE ALSO
http://doc.trolltech.com/qvalidator.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page
(qvalidator.3qt) and the Qt version (2.3.1).
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