Racketでファイル名入力ダイアログ

get-file関数でファイル名入力ダイアログを利用できます.戻り値はパスまたは#fです.
オブジェクト指向風にファイル名入力用テキストフィールド+ボタンをまとめたクラスを作成してみます.

#lang racket

(require racket/gui/base)

(define file-input-pane%
  (class vertical-pane%
    (init-field button-label)
    (init-field parent)
    (init-field [label #f])
    (super-new [parent parent]
               [stretchable-height #f]
               [stretchable-width #f])
    (when label
      (new message% [label label]
           [stretchable-width #t]
           [parent this]))
    (define horizontal-pane
      (new horizontal-pane% [parent this]
           [stretchable-height #f]
           [stretchable-width #f]))
    (define file-name-field
      (new text-field%
           [label ""] [parent horizontal-pane]))
    (define file-name-button
      (new button%
           [label button-label]
           [parent horizontal-pane]
           [callback
            (lambda (btn evt)
              (let ((fpath (get-file)))
                (when fpath
                  (send file-name-field set-value
                        (path->string fpath)))))]))
    (define/public (get-value)
      (send file-name-field get-value))
    (define/public (set-value value)
      (send file-name-field set-value value))))

;; test
(define frame (new frame% [label "example"]
                  [width 300]
                  [height 200]))
(new file-input-pane% [parent frame]
     [label "hello"]
     [button-label "file"])

(send frame show #t)