[fpc-pascal] how to use procedure of object in C

[OBones]

Michael Van Canneyt wrote:
>
>
> On Mon, 9 Mar 2015, Xiangrong Fang wrote:
>
>> Hi all,
>> I define a procedure like this:
>>
>> type
>>   TDataHandler = procedure(data: Pointer) of object;
>>
>> procedure SetHandler(h: TDataHandler); external cdecl;
>>
>> Now, can I implement SetHandler in a library written in C, then call 
>> h in C?
>
> IMHO Not without separate assembler code for each CPU.
>
> Michael.
How about using TMethod?

procedure DataHandler(DummySelf: Pointer; data: Pointer);
begin
   // do what you want to do, DummySelf is always nil.
end;

var
   Method: TMethod;
begin
   Method.Data := nil;
   Method.Code := @DataHandler;

   SetHandler(TDataHandler(Method));
end;