Declare a TDateTime as a Const in Delphi
Ok, my reaction is a bit late, but here's a solution for the newer Delphi's.
It uses implicit class overloaders so that records of this type can be used as if they are TDateTime variables.
TDateRec = record
year,month,day,hour,minute,second,millisecond:word;
class operator implicit(aDateRec:TDateRec):TDateTime;
class operator implicit(aDateTime:TDateTime):TDateRec; // not needed
class operator implicit(aDateRec:TDateRec):String; // not needed
class operator implicit(aDateRec:String):TDateRec; // not needed
end;
Implementation:
uses DateUtils;
class operator TDateRec.Implicit(aDateRec:TDateRec):TDateTime;
begin
with aDateRec do // Yeah that's right you wankers. I like "with" :)
Result := encodeDateTime(Year,Month,Day,Hour,Minute,Second,Millisecond);
end;
class operator TDateRec.Implicit(aDateTime:TDateTime):TDateRec;
begin
with Result do
DecodeDateTime(aDateTime,Year,Month,Day,Hour,Minute,Second,Millisecond);
end;
class operator TDateRec.Implicit(aDateRec:TDateRec):String;
begin
Result := DateTimeToStr(aDateRec)
end;
class operator TDateRec.Implicit(aDateRec:String):TDateRec;
begin
Result := StrToDateTime(aDateRec)
end;
Now you can declare your dates like this:
const
Date1:TDateRec=(Year:2009;month:05;day:11);
Date2:TDateRec=(Year:2009;month:05;day:11;hour:05);
Date3:TDateRec=(Year:2009;month:05;day:11;hour:05;minute:00);
To see if it works, execute the following:
ShowMessage(Date1); // it can act like a string
ShowMessage(DateToStr(Date1)); // it can act like a date
If you really want to replace all your TdateTime variables with this, you probably need to overload some other operators too (Add, subtract, explicit, ...).
The only? possible way, but probably not what you are looking for:
const
{$J+}
Expire: TDateTime = 0;
{$J-}
initialization
Expire := EncodeDate(2009, 3, 23);