GUI switching panels

gistfile1.rkt

#lang racket/gui

(define frame (make-object frame% "top"))
(define parent-panel (make-object panel% frame))
(define panel1 (make-object panel% parent-panel))
(define panel2 (make-object panel% parent-panel))

(send parent-panel delete-child panel2)
(new button% 
     [label "Switch to 2"]
     [parent panel1]
     [callback
      (lambda (b e)
        (cond [(eq? (send e get-event-type) 'button)
               (send parent-panel delete-child panel1)
               (send parent-panel add-child panel2)]
              [else (void)]))])

(new button% 
     [label "Switch to 1"]
     [parent panel2]
     [callback
      (lambda (b e)
        (cond [(eq? (send e get-event-type) 'button)
               (send parent-panel delete-child panel2)
               (send parent-panel add-child panel1)]
              [else (void)]))])

(send frame show #t)