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Use wildcard to compare string and validate input

, 3 Feb 2005
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This article describes how to use wildcard to make input validation in CEdit control or to compare string with wildcard.

Introduction

This article was inspired by Jack Handy (Wildcard string compare).

It describes a function to compare strings with wildcards. I have modified Jack's function to use MFC and use optional character in the wildcard string.

Wildcard sample

If you want to check a string like 'test' or 'tet', you may use the wildcard like this : te^st where ^ indicates an optional char.

I included another parameter to limit characters used in wildcard * or ?.

<PRE lang=c++>if (WildMatch("^-*?^.*", sValue, "0123456789")) { MessageBox("OK you have a real"); } else { MessageBox("Not a real"); }

This sample validates the string in sValue has a good format to be a real number.

Function code

<PRE lang=c++>BOOL WildMatch(CString sWild, CString sString, CString sLimitChar) { BOOL bAny = FALSE; BOOL bNextIsOptional = FALSE; BOOL bAutorizedChar = TRUE; int i=0; int j=0; // Check all the string char by char while (i<sString.GetLength()) { // Check index for array overflow if (j<sWild.GetLength()) { // Manage '*' in the wildcard if (sWild[j]=='*') { // Go to next character in the wildcard j++; // Enf of the string and wildcard end // with *, only test string validity if (j>=sWild.GetLength()) { // Check end of the string while (!sLimitChar.IsEmpty() && i<sString.GetLength()) { // If this char is not ok, return false if (sLimitChar.Find(sString[i])<0) return FALSE; i++; } return TRUE; } bAny = TRUE; bNextIsOptional = FALSE; } else { // Optional char in the wildcard if (sWild[j]=='^') { // Go to next char in the wildcard and indicate // that the next is optional j++; bNextIsOptional = TRUE; } else { bAutorizedChar = ((sLimitChar.IsEmpty()) || (sLimitChar.Find(sString[i])>=0)); // IF : if (// Current char match the wildcard sWild[j] == sString[i] // '?' is used and current char is in autorized char list || (sWild[j] == '?' && bAutorizedChar) // Char is optional and it's not in the string // and it's necessary to test if '*' make any // char browsing || (bNextIsOptional && !(bAny && bAutorizedChar))) { // If current char match wildcard, // we stop for any char browsing if (sWild[j] == sString[i]) bAny = FALSE; // If it's not an optional char who is not present, // go to next if (sWild[j] == sString[i] || sWild[j] == '?') i++; j++; bNextIsOptional = FALSE; } else // If we are in any char browsing ('*') // and curent char is autorized if (bAny && bAutorizedChar) // Go to next i++; else return FALSE; } } } else // End of the wildcard but not the // end of the string => // not matching return FALSE; } if (j<sWild.GetLength() && sWild[j]=='^') { bNextIsOptional = TRUE; j++; } // If the string is shorter than wildcard // we test end of the // wildcard to check matching while ((j<sWild.GetLength() && sWild[j]=='*') || bNextIsOptional) { j++; bNextIsOptional = FALSE; if (j<sWild.GetLength() && sWild[j]=='^') { bNextIsOptional = TRUE; j++; } } return j>=sWild.GetLength(); }

CEdit input validation

This sample shows you how to use this function to control input validation in a dynamic way.

Be careful when you define your wildcard, because it must be always true! If you want more advanced testing, don't test in real time but do only when the user validates.

For example, if you use ^-?*^.*, the user can never put the minus sign first, because '?' specifies one char is always necessary!

You can put this code in the OnChar of your CEdit child class, or if you don't want to derive a new class, you can put it in the PreTranslateMessage of the mother window, like:

<PRE lang=c++>if (pMsg->message==WM_CHAR && pMsg->hwnd==pEdit->m_hWnd && pMsg->wParam>=32) { // Define parameters CString sSaveText=""; CString sNewText=""; CString sLimitChar="0123456789"; CString sWildCard="^-*^.*"; int iNbMaxChar = 10; // If we use only upper case, makeupper if (m_bMakeUpper) pMsg->wParam = toupper(pMsg->wParam); DWORD dwSaveSel = pEdit->GetSel(); pEdit->GetWindowText(sSaveText); // Transmit this char to the CEdit to process it pEdit->SendMessage(WM_CHAR, pMsg->wParam, pMsg->lParam); pEdit->GetWindowText(sNewText); // Check if new text is ok if (!WildMatch(m_sWildCard, sNewText, sLimitChar) || sNewText.GetLength()>iNbMaxChar) { // if not, rollback pEdit->SetWindowText(sSaveText); pEdit->SetSel(dwSaveSel); } }

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

DarkYoda M
Web Developer
France France
I'm a French Industrial Developer,

I like codeproject! It help me to solve my problems many times...

I'm interresting in electronic an embedded module like snap (www.imsys.se), but I don't have any time to go hard in this way Wink | ;)

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Comments and Discussions

 
GeneralThere is an easy way... Pin
Yulianto AKA goodmast3r3-Feb-05 15:17
memberYulianto AKA goodmast3r3-Feb-05 15:17 
GeneralRe: There is an easy way... Pin
DarkYoda Mickael3-Feb-05 22:11
memberDarkYoda Mickael3-Feb-05 22:11 
GeneralRe: There is an easy way... Pin
Yulianto AKA goodmast3r4-Feb-05 16:01
memberYulianto AKA goodmast3r4-Feb-05 16:01 
Eh, could you comments your article in English.Smile | :)


<italic>Work hard and a bit of luck is the key to success.
You don`t need to be genius, to be rich.
GeneralRe: There is an easy way... Pin
DarkYoda M4-Feb-05 22:22
memberDarkYoda M4-Feb-05 22:22 

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