[fpc-pascal] How to instantiate a public type in a generic class

[luciano de souza]

Sven,

I really thoght that I had replied your message, but now, I realize I
didn't do it.

Actually, the fact compiler does not  support the sintax I proposed,
it's not very severe. In stead of passing a subtype, I can firstly
create a type from the subtype and using it in the specialization:

TPersons = TdgOPFentity.Tentities;

Passing TPersons, the compiler will not complain.

But, say me: is the problem I faced related to 2.4 version? In newer
version, would it be possible to use something like I have proposed or
will the same behviour be maintained?



2015-05-17 15:46 GMT-03:00, luciano de souza <luchyanus at gmail.com>:
> Hello listers,
>
> Using Freepascal 2.6.4, I have a problem about generics. In short, I
> can't specialize a class with a subtype of a type declared with
> "public type". Let me try to explain.
>
> In dopf.pas, I have:
>
> type
> generic TdGOpf<T1, T2, T3> = class(TdComponent)
> public type
> TEntities = specialize TFPGObjectList<T3>
> end;;
>
> If personmapper is a class specialized from TdGOpf, an instance can be
> created as follows:
>
> Personmapper := TPersonMapper.TEntities.create;
>
> Yes, this code is successul. But this code is not:
>
> type
> generic TGAction <t1, t2> = class(specialize TBrookGAction <t1>);
> private
> Fentities: t2.TEntities; //Error in type definition
> end;
>
> This code failed, so I tried:
>
> type
> generic TGAction <t1, t2> = class(specialize TBrookGAction <t1>);
> public type TCEntities = t2.Tentities; //Error in type definition
> end;
>
> I got also an error if I try:
>
> type
> generic TGAction <t1, t2, t2.TEntities> = class(specialize TBrookGAction
> <t1>);
>
> Well, I think the problem is illustrated. The doubt is how can create
> an instance of a public type, in my case, t2.Tentities inside my
> specialized class?
>
> Best regards,
>
>
> --
> Luciano de Souza
>


-- 
Luciano de Souza