在球拍中为类添加类型注释

Question

试图完成Conway's Game of Life in Racket的实现，我正在为所有内容添加类型。我有麻烦弄清楚我究竟需要做什么才能从gui库中正确键入类。

(: new-timer (Instance Timer%))
(define new-timer (new timer% [interval 400]
[notify-callback (lambda () (begin
(set-field! grd cv (next-grid (get-field grd cv) ROW COLUMNS))
(send cv on-paint)))]))
(: new-canvas% Canvas%)
(define new-canvas% (class canvas%
(super-new)
(inherit get-dc suspend-flush resume-flush)
(field [dc : (Instance DC<%>) (get-dc)] [grd : Grid (make-grid ROW COLUMNS)])
(define/override (on-char char)
(let ([event (send char get-key-code)])
(cond
[(and (char? event) (char=? event #space)) (send new-timer stop)])))

(define/override (on-paint)
(send dc erase)
(suspend-flush)
(render-grid grd ROW COLUMNS dc)
(resume-flush))))
(: cv (Instance Canvas%))
(define cv (new new-canvas% [parent main-frame]))

我在

下面得到这个错误

/Documents/conways-game-of-life/main.rkt:49:83: Type Checker: type mismatch;
;  the object is missing an expected field
;   field: grd
;   object type: (Instance Canvas%)
;   in: (get-field grd cv)
; Context:
;  /usr/share/racket/collects/racket/promise.rkt:128:5
; /home/diego/Documents/conways-game-of-life/main.rkt:49:53: Type Checker: type mismatch;
;  expected an object with field grd
;   given: (Instance Canvas%)
;   in: (set-field! grd cv (next-grid (get-field grd cv) ROW COLUMNS))

我认为这是因为画布通常没有一个网格域，但每次我试图给我的画布类型声明(: cv (Instance new-canvas%))它说它是未绑定的。完整的文件和所有的代码可以在这里找到。有人有什么想法吗?

Answer 1

在new-timer的定义中，您试图获得cv的grd字段。

虽然cv是类new-canvas%的实例，但它的类型不包含该字段。您需要为new-canvas%创建一个新的Class类型。按照惯例，它应该是一个大写的版本，如New-Canvas%。

(define-type New-Canvas% (Class ....))
(: new-canvas% New-Canvas%)
(define new-canvas% (class ....))
(: cv (Instance New-Canvas%))
(define cv (new .....))

使用Class定义的New-Canvas%类型应该指定新字段grd，并指定它是Canvas%的子类。