[Gambas-user] How to verify a date like dd/mm/yyyy?

[Richard]

On Friday 21 March 2008 14:44:51 Richard wrote:
> On Friday 21 March 2008 12:57:04 Richard wrote:
> > On Friday 21 March 2008 07:51:48 andy2 wrote:
> > > in Php i found the following script. My problem is to replicate the
> > > ereg function.
> > >
> > > FUNCTION ControlloData($data){
> > >   If(!ereg("^[0-9]{2}/[0-9]{2}/[0-9]{4}$", $data)){
> > >     RETURN FALSE;
> > >   } ELSE {
> > >     $arrayData = explode("/", $data);
> > >     $Giorno = $arrayData[0];
> > >     $Mese = $arrayData[1];
> > >     $Anno = $arrayData[2];
> > >     If(!checkdate($Mese, $Giorno, $Anno)){
> > >       RETURN FALSE;
> > >     } ELSE {
> > >       RETURN TRUE;
> > >     }
> > >   }
> > > }
> > >
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> >
> > You could also do something similar to the PHP code:
> >
> > PUBLIC FUNCTION is_date(data AS String) AS Boolean
> > DIM aDateElements AS String[]
> > DIM iDay AS Integer
> > DIM iMth AS Integer
> > DIM iYear AS Integer
> >
> >     IF NOT (data LIKE "[0-9][0-9]/[0-9][0-9]/[0-9][0-9][0-9][0-9]") THEN
> >         RETURN FALSE
> >     ELSE
> >         aDateElements = Split(data, "/")
> >         iDay = aDateElements[0]
> >         iMth = aDateElements[1]
> >         iYear = aDateElements[2]
> >         TRY RETURN IsDate(Date(iYear, iMth, iDay))
> >         IF ERROR THEN RETURN FALSE
> >     ENDIF
> >
> > END
> >
> > The Gambas LIKE operator is just as weak as the VB one and the mask I
> > have shown will only check for digits. It will accept digits which do not
> > make up a date (eg 72/33/1234); this is the same behaviour as your PHP
> > regular expression.
> >
> >
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>
> I suppose, in deference to the peculiar requirements of our northern
> trans-atlantic brethren I should have taken more care in the example to
> make it locale-aware.
>
> The trick, which I found when looking at the ValueBox code, is to construct
> a localised version of the YYYY MM DD format string for a gb.ShortDate.
> When we are extracting day and month from the array of date element values
> we must know which one is the day and which the month.
>
> Benoit did it something like this:
>
>   sDateFormat = Format(Date(3333, 11, 22), gb.ShortDate)
>
> so now the month is represented by 11 and the day by 22. All we need to do
> is check what the first two digits represent by looking at our date format
> variable before we fetch values from the array.
>
> PUBLIC FUNCTION is_date(data AS String) AS Boolean
> DIM aDateElements AS String[]
> DIM iDay AS Integer
> DIM iMth AS Integer
> DIM iYear AS Integer
> DIM $sDateFormat AS String
>
>     sDateFormat = Format(Date(3333, 11, 22), gb.ShortDate)
>
>     IF NOT (data LIKE "[0-9][0-9]/[0-9][0-9]/[0-9][0-9][0-9][0-9]") THEN
>         RETURN FALSE
>     ELSE
>         aDateElements = Split(data, "/")
>         iDay =
> IIF(LEFT(sDateFormat,2)="22",aDateElements[0],aDateElements[1]) iMth =
> IIF(LEFT(sDateFormat,2)="11",aDateElements[0],aDateElements[1]) iYear =
> aDateElements[2]
>         TRY RETURN IsDate(Date(iYear, iMth, iDay))
>         IF ERROR THEN RETURN FALSE
>     ENDIF
>
> END
>
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> Defy all challenges. Microsoft(R) Visual Studio 2008.
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> Gambas-user mailing list
> Gambas-user at lists.sourceforge.net
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One more attempt to get it right...
 
I overlooked the assumption about the date format in the LIKE expression and 
the possibility to tighten up the comparison mask to make it a little more 
robust (not much).

PUBLIC FUNCTION is_date(data AS String) AS Boolean
DIM aDateElements AS String[]
DIM iDay AS Integer
DIM iMth AS Integer
DIM iYear AS Integer
DIM sDateFormat AS String
DIM sMask AS String

    sDateFormat = Format(Date(3333, 11, 22), gb.ShortDate)

    IF LEFT(sDateFormat,2)="22" THEN
	sMask = "[0-3][0-9]/[0-1][0-9]/[0-9][0-9][0-9][0-9]"
    ELSE
	sMask = "[0-1][0-9]/[0-3][0-9]/[0-9][0-9][0-9][0-9]"
    ENDIF

    IF NOT (data LIKE sMask) THEN
        RETURN FALSE
    ELSE
        aDateElements = Split(data, "/")
        iDay = IIF(LEFT(sDateFormat,2)="22",aDateElements[0],aDateElements[1])
        iMth =IIF(LEFT(sDateFormat,2)="11",aDateElements[0],aDateElements[1]) 
	iYear = aDateElements[2]
        TRY RETURN IsDate(Date(iYear, iMth, iDay))
        IF ERROR THEN RETURN FALSE
    ENDIF

END


Richard