RE: [sv-ec] Explicitly typed constructors?

Jonathan,

You can get what you want by creating a static method that call the
constructor ('new' is already a special static method).

class D1 extends Base;
...
static function D1 knew;
	D1 = new();
endfunction
endclass
class D2 extends Base;
...
static function D2 knew;
	D2 = new();
endfunction
endclass


Then this code will do what you want.

  b = D1::knew();
  b.v();
  b = D2::knew();
  b.v();


This will work better than casting the constructor because it will be
able to deal with the possible differences in arguments to the
constructors of the derived classes.

Dave


-----Original Message-----
From: owner-sv-ec@server.eda.org [mailto:owner-sv-ec@server.eda.org] On
Behalf Of Jonathan Bromley
Sent: Friday, August 03, 2007 8:51 AM
To: sv-ec@server.eda-stds.org
Subject: [sv-ec] Explicitly typed constructors?

hi sv-ec,

In some recent work I've frequently encountered the situation
that I have a variable of base class type, but wish to be
able to construct objects of various derived types and use 
the common base variable to reference them.  To construct the 
derived objects, I need a derived-type variable (don't I?):

  class Base; 
    .... 
    virtual function void v(); ...
    ....
  endclass : Base
  class D1 extends Base; .... endclass
  class D2 extends Base; .... endclass
  ....
  Base b;
  D1 d1;
  D2 d2;
  ....
  d1 = new;
  b = d1;
  b.v();
  ....
  d2 = new;
  b = d2;
  b.v();

It would be very nice if I could force new() to create 
an object of a derived-class type even though the result 
of new() is then assigned immediately to a base-class 
variable: something like

  b = D1::new();
  b.v();
  b = D2::new(); 
  b.v();

Or, maybe,

  b = D1'new();

Either way, the idea is to mirror Java's

  b = new D1();

Has this already been dismissed for some reason?
I'm no OOP guru, but I can't see any killer reason
why it should be unreasonable.

Thanks
-- 
Jonathan Bromley, Consultant

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