Input Validation And Regular Expressions Ch 14 PDF

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Summary

xInput ValiRegular Eation andpressionsCOS3711 - e-TutorPowerpoint Ch 14Outline Input Masks Validators Regular Expressions w A QLineEdit object provides a Mask for the input A mask is a special string that tellsthe line edit what type of characters the user can type next. If a user types a character ...

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Input Vali ation and Regular Expressions COS3711 - e-Tutor Powerpoint Ch 14

Outline • Input Masks • Validators • Regular Expressions

Input Marks • Control what is typed in an input idget by the user

• A QLineEdit object provides a Mask for the input • A mask is a special string that tells wthe line edit what type of characters the user can type next. If a user types a character that is not in range, it is simply ignored by the line edit. • A mask has both normal characters and special character. • The following code creates a QLineEdit that takes a numeric value in the form: 1234-123-1234-123 (four digits, then a dash, then 3 digits, another dash, four more digits, a dash and end with 3 digits):

Input Masks (Cont.) #include #include int main(int argc, char *argv[]){ QApplication app(argc, argv); QLineEdit e; e.setInputMask("9999-999-9999-9 9"); e.show(); return app.exec(); }

• Masks are useful for inputs with rigid formats such as IP addresses and serial numbers. For more complex inputs, a more flexible solution is needed: validators.

Validators • Objects that can be attached to input widgets such as QLineEdit, QComboBox, and QSpinBox to validate user input

• Implemented with the QValidator class • QValidator class provides three important subclasses QIntValidator, QDoubleValidator and QRegExpValidator for input validation • QIntValidator - validates integer values, • QDoubleValidator - validates floating point values and • QRegExpValidator - validates anytext using regular expression • The following code creates an integer only line edit using a validator, i.e., an example of use of QIntValidator

Validators (Cont.) #include #include #include int main(int argc, char *argv[]){ QApplication app(argc, argv); QLineEdit e; QIntValidator *v = new QIntValidator(0, 100); e.setValidator( v );//a QIntValidator is set a validator in a QLineEdit e.show(); return app.exec(); }

• The above code implements a line edit that allows only integers between 0 and 100.

Validators (Cont.) • QRegExpValidator is a flexible validator • QRegExpValidator accepts a regular expression and use it to validate any input text in a QLineEdit

• The following code implements a QLineEdit that accepts only valid names #include int main(int argc, char *argv[]){ QApplication app(argc, argv); QLineEdit e; QRegExp re("[_a-zA-Z][_a-zA-Z0-9]+"); QRegExpValidator *v = new QRegExpValidator(re); e.setValidator( v ); e.show(); return app.exec(); }...