LUFDOC : strfiltertips

Notes

The strfilter.pas unit is a simple validation unit that checks many common inputs for simple correctness.

Example Situation 1

If you have a web form and you wish to check the incoming POST/GET variable and ensure it is a number. Simply call GetCgiVar from the powerful web utilities main unit, then you use the IsNum function from strfilter.pas to verify it is numeric input.

var
  posted: string;
begin
  posted:= GetCgiVar('phone'); // posted from a form edit box with NAME='phone'
  if (IsNum(posted)) and (posted <= 16) then // accept phone number under 16
    webwrite('Thank you, phone number accepted.')
  else
    webwrite('Phone number must not contain dashes or brackets.' + 
             'and must be shorter than 16 numbers long please.')  
end.

In the above example, we check to see if the input is close to a correct phone number. Since some folks may live in countries with different length phone numbers, it is hard to verify the phone number is one hundred percent correct, so we just ensure that the phone number entered is under 16 characters and contains only numbers.

See also the IsNumSpace which allows numbers and spaces, and the IsNumSpaceDashBrack which allows numbers, dashes, and brackets. For database integrity, you might want to stick with numbers only.

Example Situation 2

If you have a web form and you are validating an Email address for general correctness, you can use the IsEmail function.

var
  posted: string;
begin
  // get a variable through POST/GET using GetCgiVar_S (security bypass). We allow 
  // '@' symbol and '.' symbol in so we specify zero security as paramater
  posted:= GetCgiVar_S('email', 0); // posted from a form edit box with NAME='email'
  if IsEmail(posted) then
    webwrite('Thank you, email address accepted.');
end.

Download strfilter.pas

This unit is part of the general-utilities download group and is available on SVN and sourceforge.

Some documentation

This unit hasn't been documented yet but below are some comments and it is pretty straightforward to use the unit.

Sample functions and descriptions from the strfilter.pas unit are below:


// checks string for characters given as a parameter 
function ValidChars(s: string; CharSet: TCharSet): boolean;

// Checks if email address format is correct or extremely close to correct. It is
// impossible to check to see whether the email is 100 percent correct since new
// domain name extensions are being added every year (.ws, .tk, .co.uk.org). 
// Does not use a whitelist. Just checks for general "within the ballpark" 
// correctness. Does not accept address such as John@localhost it must be in the 
// format john@domain.com or john.domain.ca etc.}
function IsEmail(s: string): boolean;

// alphabet and numbers only allowed
function IsAlphNum(s: string): boolean;

// alphabet, numbers, and space allowed
function IsAlphNumSpace(s: string): boolean;

// alphabet, numbers, space, and underscore allowed
function IsAlphNumSpaceUscor(s: string): boolean;

// alphabet, numbers, space, dash, and underscore allowed
function IsAlphNumSpaceDashUscor(s: string): boolean;

// alphabet, numbers, dash, and underscore allowed
function IsAlphNumDashUscor(s: string): boolean;

// alphabet, numbers, and underscore allowed
function IsAlphNumUscor(s: string): boolean;

// alphabet, numbers, and dash allowed
function IsAlphNumDash(s: string): boolean;

// numbers, dashes, brackets, plus sign allowed
function IsNumDashBrackPlus(s: string): boolean; 

// numbers, dashes, brackets allowed
function IsNumDashBrack(s: string): boolean; 

// numbers only
function IsNum(s: string): boolean;

// numbers and dashes allowed
function IsNumDash(s: string): boolean;

// numbers and spaces allowed
function IsNumSpace(s: string): boolean;

// numbers, dashes, and spaces allowed
function IsNumDashSpace(s: string): boolean;

// numbers, dashes, brackets, and spaces allowed
function IsNumSpaceDashBrack(s: string): boolean;

// alphabet only allowed (a..z  A..Z)
function IsAlph(s: string): boolean;

// alphabet plus underscore and space allowed
function IsAlphSpaceUscor(s: string): boolean;

// alphabet plus dashes allowed
function IsAlphDash(s: string): boolean;

// alphabet plus dashes and spaces allowed
function IsAlphDashSpace(s: string): boolean;

// alphabet plus underscore allowed
function IsAlphUscor(s: string): boolean;

// alphabet plus space allowed
function IsAlphSpace(s: string): boolean;

// lower case alphabet allowed
function IsLowAlph(s: string): boolean;

// lower case alphabet plus space allowed
function IsLowAlphSpace(s: string): boolean;

// lower case alphabet plus underscore allowed
function IsLowAlphUscor(s: string): boolean;

// lower case alphabet plus space and underscore allowed
function IsLowAlphSpaceUscor(s: string): boolean;

// upper case alphabet allowed
function IsUpAlph(s: string): boolean;

// upper case alphabet and underscore allowed
function IsUpAlphUscor(s: string): boolean;

// upper case alphabet and space allowed
function IsUpAlphSpace(s: string): boolean;

// upper case alphabet, and underscores and spaces allowed
function IsUpAlphSpaceUscor(s: string): boolean;