Am 30.01.2013 18:18, schrieb dennis luehring:
Am 30.01.2013 17:16, schrieb Eko Wahyudin:
thanks all,
I think i am understand, if the closest solution is template,
there is no solution in D for my code like this.
type
TMyObjectClass = class of TMyObjectA;
var
ClassArray : array of TMyObjectClass; //the content
initialized
randomly
ObjectArray : array of TMyObjectA;
i, j : Integer;
procedure CreateAllObject;
begin
J:= length(ClassArray);
for I:= 0 to J do begin
ObjectArray[I]:= ClassArray[I].Create({some argument});
end;
end;
if D unable to do this, I think we must do something with D.
I'm still thinking, why constructor in D adopt C++ style rather
than pascal style, while pascal style is better :-?
sorry but the pascal "class of"-type and the ctor-derivation isn't that
super-mighty at all
as long as the ctors of your object are the same everything is fine
else -> the feature isn't useable anymore, then you need a real object
factory
in real OOP objects are specialized through its virtual method
implementations AND its ctor-parameters (which are similar in very very
few rare cases)
for example pseudo code
class Stream
virtual read_bytes()...
class FileStream: Stream
this(filename)
class NetworkStream: Stream
this(tcp_ip,timeout)
Stream[] streams
streams ~= FileStream("c:/temp/test.txt");
streams ~= NetworkStream("123.112.2.1", 1000);
stream[n].read_bytes()
this is a much more common OOP/ctor situation then yours
i think its part of pascal/object delphi to ease the VCL development
but this can be easily reached with an internal CreateInstance routine like
Stream
virtual Stream CreateInstance()
and
FileStream implements CreateInstance() with with return new FileStream
NetworkStream "" with new NetworkStream etc.
so whats the realy big deal/feature of this "class of"-type except for
very trivial OOP case
Actually there are many definitions what real OOP means.
As for Delphi's case, if I am not mistaken it tries to follow the
metaclass concept that Smalltalk has, and Java/.NET have to a certain
extent.
You can do lots of cool tricks with metaclass programming, specially in
Smalltalk.
--
Paulo
