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

[Richard]

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