first generic attempt

[Paolo]

Maybe it is not possible.
Starting palying with generics I have an object that is something like (code reduced to the essential parts)

Code: Pascal  [Select][+][-]

1. TFirstGeneric <T1>=class
2. Private
3. ..
4.    A:T1;
5. ..
6. End;
7.  

My need is to play with T1 both integer and double type.
 
Everything is going well up to the point I need to do a conversion from an input string, and I have to properly select one of the two alternatives

Code: Pascal  [Select][+][-]

1.  
2. (S is a string)
3. ..
4. A:=S.ToInteger;
5. A:=S.ToDouble;
6. ..
7.  

How can do that ?
alternatives ?

[avk]

Maybe

Code: Pascal  [Select][+][-]

1. ...
2. uses
3.   ... SysUtils, ...
4. ...
5.   A := T1.Parse(S);
6. ...
7.  

[Paolo]

thanks. What PARSE do ? nothing found in SysUtils.

[TRon]

thanks. What PARSE do ? nothing found in SysUtils.

Helpers: https://www.freepascal.org/docs-html/rtl/sysutils/typehelpers.html

in particular: https://www.freepascal.org/docs-html/rtl/sysutils/tstringhelper.parse.html

[Paolo]

Thank you !

[avk]

More precisely LongInt.Parse()/Integer.Parse() and Double.Parse().

[TRon]

Yeah, sorry avk and Paolo as I interpreted the question the other way around (convert to string).

links:
https://www.freepascal.org/docs-html/rtl/sysutils/tdoublehelper.parse.html
https://www.freepascal.org/docs-html/rtl/sysutils/tintegerhelper.parse.html

[Martin_fr]

Code: Pascal  [Select][+][-]

1. generic TFirstGeneric <T1>=class
2.   function ParseString(s:string): T1; virtual; abstract;
3. end;
4.  
5. TFoo = class(specialize TFirstGeneric<single>)
6.   function ParseString(s:string): single; override;
7. end;
8.  

If you must do it in the base, maybe this will help (not the nicest code in my opinion....)

Code: Pascal  [Select][+][-]

1.   if TypeInfo(T1) = TypeInfo(Single) then writeln('s');
2.   if TypeInfo(T1) = TypeInfo(Double) then writeln('d');
3.  

[Paolo]

Thaks to all for the suggestions. I think I'll rearrange the code logic (same problem to distinguish between 'div' and '/'

[Paolo]

still unable to find PARSE, even if the code compiles (but not yet tested)

[TRon]

still unable to find PARSE, even if the code compiles (but not yet tested)

Honest question: what did you not understood from typehelpers located at sysutils ? It is fundamental to know about typehelpers in order to understand how it works.

[Paolo]

Forget it, now I see where they are, thank you