[plt-scheme] levels of access to object fields

At Thu, 18 Jan 2007 06:33:49 -0500, Prabhakar Ragde wrote:
> Is it possible to make a field of an object that is accessible to 
> objects of the same class but otherwise private? I think I can do this 
> in awkward ways (e.g. defining a struct within the class and wrapping 
> the field in it). Is there a clean way? Thanks. --PR

Use `define-local-member-name':

 (define c%
   (let ()
     (define-local-member-name m) ; confines `m' to inside the `let'
     (class object%
       (init-field x)
       
       (define/public (m) x)
       
       (define/public (get-other o) (send o m))
      
       (super-new))))

 (define a (new c% [x 1]))
 (define b (new c% [x 2]))
 (send a get-other b) ; => 2
 (send b m) ; => no such method "m"


Matthew