Am 30.10.2013 10:36, schrieb Michael Van Canneyt:
On Wed, 30 Oct 2013, Sven Barth wrote:
Am 30.10.2013 08:47, schrieb Xiangrong Fang:
Hi All,
I have the following class:
type
generic TVector<T> = class
private type
TDataType = array of T;
private
FData: TDataType;
... ...
public
... ...
function Slice(APos: Integer = -1; ACount: Integer = -1):
TDataType;
end;
The Slice() method return a portion of the data as a dynamic array.
My question is, as I define TDataType as PRIVATE type, why it is
still usable outside of the class? In the main program
I did:
type
TIntVector = specialize TVector<Integer>;
var
iv: TIntVector;
ia: array of Integer;
begin
iv := TIntVector.Create;
... ...
ia := iv.Slice;
end.
This will assign a TDataType (is it TVector$TDataType or
TIntVector$TDataType? I don't know) to an "array of Integer".
Why this assignment works?
i.e. how does the type system work?!
It's a bit annoying that the usage private/protected types in
public/published functions is allowed... (this is however Delphi
compatible) Maybe this should be adjusted for non-Delphi modes for
language consistency... (maybe at least as a warning which
could be elevated to an error if someone wants)
I think it is an error. You declare something as private, and then you
use it in a public function ? If that is not a visibility clash, I
don't know what is :)
I agree, but the question is should we declare this as a bug in the
language and thus fix it which might lead to adjustments of legacy
(2.6.x) code or use a warning. I personally would do the former (and
better sooner than later). We need to keep the current behavior in mode
Delphi however... (Note: Delphi additionally allows to access protected
types from external units; could be related to the point that helper
types allow access to protected types and fields as well...)
Regards,
Sven
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