[fpc-pascal] constructor as procvar

[Michael Van Canneyt]

On Sat, 20 Mar 2010, David Emerson wrote:

> How can I obtain a class type variable from an instance? I want to
> create a second instance of the same descendant class (via the
> constructor, which will take some parameters and make the new instance
> unique)

Try using Instance.ClassType. Something like:

Var
   C : t_mammal_class;
   MyClone : T_mammal;

begin
   C:=t_mammal_class(Instance.ClassType);
   MyClone:=C.Create;
end;


Michael.


>
> Tobject.classtype returns TClass (class of TObject) which I first
> assumed would work great. However I cannot seem to do a type conversion
> from TClass to t_mammal_class (class of t_mammal)! So I am stuck here.
>
> I tried just using TClass and skipping t_mammal_class, but then I can't
> use my overriden constructor that takes special parameters.
>
> Thanks in advance,
> David.
>
>
> On Fri 19 Mar 2010, David Emerson wrote:
>> Florian Klaempfl wrote:
>>> Constructor procvars are indeed not supported but the way to achieve
>>> what you want is to use class type variables
>>>
>>>   t_mammal_class = class of t_mammal;
>>>
>>>   function find_or_create_animal (color : byte;
>>>       pass_mammal_type : t_mammal_class) : t_mammal;
>>>
>>>   brown_pig := t_pig (pig_pen.find_or_create_animal (brown, t_pig));
>>
>> ah, that is exactly what I need. Works perfectly. Thanks much.
>>
>> ~D.
>>
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>
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