[fpc-pascal] Initialize object variables

Sven Barth pascaldragon at googlemail.com
Thu Apr 28 15:47:05 CEST 2011


Am 28.04.2011 11:33, schrieb Howard Page-Clark:
> On 28/4/11 10:00, J├╝rgen Hestermann wrote:
>>
>>
>> Darius Blaszyk schrieb:
>>> Is there any way to initialize object variables, other than writing an
>>> init method?
>>> So something like:
>>> myobj = object
>>> myvar: word = $ffff;
>>> end;
>> I don't think so.
>> An object is a pointer to a data structure on the heap.
>> At compile time, this data structure is not yet allocated.
>>
>> _______________________________________________
>> fpc-pascal maillist - fpc-pascal at lists.freepascal.org
>> http://lists.freepascal.org/mailman/listinfo/fpc-pascal
>>
> I think objects are allocated on the stack (not the heap), but that does
> not help in circumventing the init method to initialize them.

Yes, they are on the stack and yes that makes a difference:

=== source begin ===

type
   TMyObject = object
     i: Integer;
     s: String;
   end;

procedure Test;
var
   a: TMyObject = (
        i: 42;
        s: 'Foo';
begin
   Writeln(a.i);
   Writeln(a.s);
end;

=== source end ===

A call to "Test" will print

=== output begin ===
42
Foo
=== output end ===

This works with records (and primitive types) as well (it does not work 
in Delphi though as Delphi does not allow initialization of local variables)

Regards,
Sven



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