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Date: Tue, 2 Sep 2003 14:45:37 +0100
To: caml-list@inria.fr
Subject: [Caml-list] Alternate constructors for a class
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From: Richard Jones <rich@annexia.org>
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I have a class defined currently like this:

  class view ?width ?height ?packing ?show ?(title = "untitled") () =
    (* ... *)

I want to provide an alternate way of constructing this class, in this
case by unmarshalling it from a channel (using the Marshall module).
Callers should be able to construct a view either using the explicit
parameters, or by doing:

  let chan = open_in_bin "serialized_class" in
  let view = new view ~chan in
  (* ... *)

Now in the case above I guess I could add an extra optional ?chan
argument, but that seems a bit ugly because it doesn't prevent users
from supplying incorrectly both ~chan and ~title, for example.

Is there an easy way to provide two different constructors for a
class?

Other languages do allow different sets of arguments to different
constructors for the same class quite naturally.

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://freshmeat.net/users/rwmj
Merjis Ltd. http://www.merjis.com/ - all your business data are belong to you.
"I wish more software used text based configuration files!"
 -- A Windows NT user, quoted on Slashdot.

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