Thanks Danny, that's a step in the direction I wanted to go. But on further reflection, I think what I was looking for (i.e. have some class that stops it's own instantiation and defers to another class depending on some parameter value(s)) doesn't really make sense. Instead I need some sort of factory function that contains the conditionals and that returns an instance of the right class.
Cheers, Kieron On Jun 26, 2012, at 8:22, Danny Yoo <d...@hashcollision.org> wrote: >> The solution that springs to mind is to choose which class to instantiate >> with (if (list? param-a) ,,,) but then I'd have to state the parameter lists >> twice. > > Hi Kieron, > > > Can you choose the class using an if or cond? > > For example: > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > (define (try-it x) > > (define the-class% > (if (list? x) multi-item-representer% item-representer%)) > > (define r (new the-class% [param-a x] [param-b 50] [param-c "yellow"])) > > (send r print)) > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > This bit of code binds the-class% at runtime to one of those classes, > depending on x. ____________________ Racket Users list: http://lists.racket-lang.org/users
