[plt-scheme] MrEd question: display image-snip% in a window; deinitialization

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Thu Oct 5 23:29:42 EDT 2006

At Thu, 5 Oct 2006 21:25:13 -0600, "Chongkai Zhu" wrote:
> By "Override the `on-close' method of the frame", do you mean:
> (define my-frame%
>   (class frame%
>     (override on-close)
>     (define (on-close)
>       ;my deinitialization code here
>       (super on-close))))
> ? If yes, I get the following error message:
> class*: superclass method for override, overment, or rename-super is not 
> overrideable: on-close for class: my-frame%

I should have written "Augment the `on-close' method." That is, use
`augment' instead of `override' (and optionally use `inner' instead of


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