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Message-Id: <20060914.090040.92346078.garrigue@math.nagoya-u.ac.jp>
To: jeremy@cowgar.com
Cc: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Passing class type as parameter?
From: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
In-Reply-To: <D2466E0B-332C-4733-82AF-DF701C5C97AE@cowgar.com>
References: <D2466E0B-332C-4733-82AF-DF701C5C97AE@cowgar.com>
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X-Spam: no; 0.00; model:01 model:01 syntax:01 finder:98 finder:98 caml-list:01 constructor:01 constructor:01 inherit:01 parameter:02 garrigue:03 garrigue:03 jacques:03 jacques:03 let:03 

From: Jeremy Cowgar <jeremy@cowgar.com>
> Can I do something like:
> 
> class base_model = object(self)
>    method from_array ary = ...
> end ;;
> 
> class user = object(self)
>    inherit base_model
>    ...
> end ;;
> 
> let finder sql class_type =
>    query_database sql ;
>    let res = new class_type in
>      res#from_array res ;;
> 
> let users = finder "SELECT * FROM users" user in
>    xxx yyy ;;
> 
> Ok. That is not working code, prob has syntax errors as well, but you  
> get my idea. The problem I am having is passing the class to the  
> generic finder method.

No, you can't, but you can pass the class constructor in place, which
is just equivalent.

let finder sql class_new =
   query_database sql ;
   let res = class_new () in
     res#from_array res ;;

let users = finder "SELECT * FROM users" (fun () -> new user) in
   xxx yyy ;;

Note that in general the class constructor takes arguments, so you
don't need the above anonymous function.

Jacques Garrigue