I’m trying to port (well actually rewrite) an application I created in C# a couple of years ago. It’s pretty simply but it has a few basic date manipulations…
Am I alone in believing that the Xojo Date class is pretty seriously lacking? There is no obvious way to do arbitrary formats (even simply things like getting a zero-padded day or month number aren’t easily achievable).
I basically have to recreate from scratch a bunch of simple functions I kind of expect to be able to perform on a date object… Are there plans to improve it? Is there an alternative class around that I haven’t found yet?
I work a lot with dates and never have any problems.
Keep in mind that the dateobject takes its format from the system date format of the computer you are working on
change the system date to the date format of your C# programme
Failing that, write a method to do that for you
then use
dim d as new date
dim bol as boolean
bol = parsedate(oldDateString, d)
Do all calculations with d.TotalSeconds
I maintain an M_Date module that adds a lot of features to Date, including the ability to do arbitrary formats with a ToString function that implements these:
I’ve included a ValidDate function written by Steve Garman that will attempt to validate a date string based on the order of the values regardless of the delimiter used, and return a date if successful. Here is the code for it:
Protected Function ValidDate(text as String, ByRef value As Date, assumePastFuture as integer= 0) As Boolean
// Written by Steve Garman
// http://rb.sgarman.net/validDate.php
// If the year provided has only one or 2 digits, check assumePastFuture
// negative value means the past, positive means future, 0 means current century
// If no year is supplied, assumePastFuture has a granularity of 1 year
Static yearPos as Integer = -9
Static monthPos as Integer = -9
Static dayPos as Integer = -9
if yearPos = -9 then // first time through
yearPos = -1 // only try this once
// try to work out local date format
// assume Gregorian calendar
// assume shortDate contains all 3 numbers
// don't use NthField or Split in case it contains other characters
dim d as new date
// clear any time numbers, in case of unusual shortDate format
d.TotalSeconds = 0
// set unique values for year, month & date
d.SQLDate = "2005-12-31"
dim s as String = d.ShortDate
dim pos() As integer
dim thisPos as Integer
thisPos = InStr( 0, s, "05" )
if thisPos > 0 then pos.Append thisPos
thisPos = InStr( 0, s, "12" )
if thisPos > 0 then pos.Append thisPos
thisPos = InStr( 0, s, "31" )
if thisPos > 0 then pos.Append thisPos
if UBound( pos ) = 2 then
// we've found all three elements
// sort them by position in shortDate
dim typ() As string = Array( "y", "m", "d" )
pos.SortWith typ
yearPos = typ.IndexOf( "y" )
monthPos = typ.IndexOf( "m" )
dayPos = typ.IndexOf( "d" )
end if
end if
if yearPos < 0 or monthPos < 0 or dayPos < 0 then
// we don't know how to parse the date
// some might want to set defaults instead of returning false
Return false
end if
// now check the date has just numbers and two delimiters
Dim sep as String
Dim tmp as String
Dim i as Integer
Dim noYearSupplied as Boolean
tmp = text
// first figure out what separator they gave us .. have to both be the same one
for i = 0 to 9
tmp = replaceAll(tmp,format(i,"0"),"")
next
select case len(tmp)
case 0
// unable to understand the format entered
return false
case 1
sep = tmp
case 2
sep = mid(tmp,1,1)
if sep <> mid(tmp,2,1) then
// invalid - two different separators
return false
end if
else
return false
end select
//make array of elements
Dim dats() as String = Split( text, sep )
if UBound( dats ) <> 2 then
// add in the missing year ?
dim tmpDate as new date
dats.Insert yearPos, format(tmpDate.year,"0000")
noYearSupplied = True
end if
if UBound( dats ) <> 2 then
//invalid date - should never get here.
Return false
end if
dim yr As integer = CDbl( dats( yearPos ) )
if yr < 100 then
// fix short year by assuming current century
// proving that we learned nothing from y2k
dim today as new Date
dim century as integer
century = today.year \\ 100
century = century * 100
yr = yr + century
// use any assumptions about whether the date is past or future to set century
if assumePastFuture < 0 then
if yr > today.Year then
yr = yr - 100
end if
elseif assumePastFuture > 0 and yr < today.Year then
yr = yr + 100
end if
dats( yearPos ) = CStr( yr )
elseif noYearSupplied then
// use any assumptions about whether the date is past or future to set year
dim mth as integer = CDbl( dats( monthPos ) )
dim dy as integer = CDbl( dats( dayPos ) )
dim today as new Date
if assumePastFuture < 0 then
if mth > today.Month or ( mth = today.Month and dy > today.Day ) then
yr = yr - 1
end if
elseif assumePastFuture > 0 and ( mth < today.Month or ( mth = today.Month and dy < today.Day ) ) then
yr = yr + 1
end if
dats( yearPos ) = CStr( yr )
end if
// put detail into a date object
dim retVal as new date
dim yy,mm,dd as Integer
yy = val( dats( yearPos ) )
mm = val( dats( monthPos ) )
dd = val( dats( dayPos ) )
retVal.TotalSeconds = 0
retVal.Year = yy
retVal.Month = mm
retVal.Day = dd
// check the date object is not making corrections
if retVal.Year <> yy or retVal.Month <> mm or retVal.Day <> dd then
//probably an invalid day of the month
Return false
end if
//populate value ( ByRef side-effect )
if value = nil Then
value = new Date
end if
value.totalseconds = retVal.TotalSeconds
return true
End Function
Thanks, I’ll give it another go. I think i’ve tried this function before but I believe if a date string is passed which is dd/mm/yyyy or mm/dd/yyyy it parses and gives preference to mm/dd/yyyy format (i.e. US Style). I may need to modify to allow this to be chosen by the user.
Again, fairly simple to achieve a similar thing in Xojo, but much more code. Overall I find, in learning Xojo/Realbasic that classes tend to have fewer helper methods usually.
dim theDate as New Date
dim tomorrow as New Date(theDate)
tomorrow.Day = tomorrow.Day + 1
dim yesterday as New Date(theDate)
yesterday.Day = yesterday.Day - 1
(even simply things like getting a zero-padded day or month number aren’t easily achievable)
Isn’t it easy ?
Can you be more specific about other “lackings”[/quote]
It’s not difficult, it just seems a little unnecessary - a basic date formatting feature is pretty handy and available in every other programming language I used (maybe not Turbo Pascal in the 90’s, I can’t remember)
[quote=17087:@Tim Hare]
dim theDate as New Date
dim tomorrow as New Date(theDate)
tomorrow.Day = tomorrow.Day + 1
dim yesterday as New Date(theDate)
yesterday.Day = yesterday.Day - 1[/quote]
Yikes, I was looking for this. This should be documented in the date class.
I was assuming it would only perform integer addition and cause an overflow (days > 31). But it just works as it should for date arithmetics.
[quote=17087:@Tim Hare]dim theDate as New Date
dim tomorrow as New Date(theDate)
tomorrow.Day = tomorrow.Day + 1
dim yesterday as New Date(theDate)
yesterday.Day = yesterday.Day - 1[/quote]
Granted, I have tested this yet, but how does that work when the modified date becomes invalid? Such as .Day + 1 on the last day of the month?
A safer way would seem to be:
Dim oneDay as Integer = 86400
Dim theDate as New Date
Dim tomorrow as New Date(theDate)
tomorrow.Seconds = tomorrow.Seconds + oneDay
It’s easy for simple things, but appears to be more difficult for more complex manipulations. Again, I’m not saying these things are impossible, I’m just a little surprised as the sparseness of some classes and functions is all.
It is possible to edit ones own post if there is no reply posted yet. However there is a bug in the Forum software, so a browser page refresh will make the edit option available in the top right corner.
[quote=17095:@Dylan Reeve]Granted, I have tested this yet, but how does that work when the modified date becomes invalid? Such as .Day + 1 on the last day of the month?
[/quote]
The month rolls seamlessly, both forward and back. Test it. The year adjusts, too, as necessary.
