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Re: Seeking Advice about refactoring and advice snippet


From: Filipe Silva
Subject: Re: Seeking Advice about refactoring and advice snippet
Date: Fri, 10 Feb 2017 14:24:16 -0200

Chunyang, thanks for the alternative approach!

I'd really like to know how to perform this simple refactoring though, just
to improve my knowledge of elisp a little bit.

[]s

Filipe

On Fri, Feb 10, 2017 at 12:17 PM, Chunyang Xu <address@hidden> wrote:

> Hi,
>
> It should be easier to use 'kill-buffer-query-functions'
>
>   (defun dont-kill-scratch ()
>     (if ((equal (buffer-name) "*scratch*"))
>         (progn (message "DENIED! don't kill my precious *scratch*!!")
>                nil)
>       t))
>
>   (add-hook 'kill-buffer-query-functions #'dont-kill-scratch)
>
> Filipe Silva writes:
>
> > Dear good people of the emacs help list,
> >
> > I have a working snippet that advices both kill-buffer and
> kill-this-buffer
> > to not kill the *scratch* buffer:
> >
> >       (defun ninrod/scratch-bodyguard (buffer-assassin &rest arguments)
> >         (let ((buffer-to-kill (buffer-name (current-buffer))))
> >           (if (equal buffer-to-kill "*scratch*")
> >               (message "DENIED! don't kill my precious *scratch*!!")
> >             (apply buffer-assassin arguments))))
> >       (defun ninrod/scratch-protection (buffer-assassin &rest arguments)
> >         (let ((buffer-to-kill (car arguments)))
> >           (if (equal buffer-to-kill "*scratch*")
> >               (message "DENIED! don't kill my precious *scratch*!!")
> >             (apply buffer-assassin arguments))))
> >       (advice-add #'kill-this-buffer :around #'ninrod/scratch-bodyguard)
> >       (advice-add #'kill-buffer :around #'ninrod/scratch-protection)
>
> Considering 'kill-this-buffer' calls 'kill-buffer', advising
> 'kill-buffer' alone is enough.
>
> > The problem is that these lines:
> >
> >       (message "DENIED! don't kill my precious *scratch*!!")
> >      (apply buffer-assassin arguments))))
> >
> > Are repeated in both functions, so I thought that I could apply the DRY
> > principle and refactor the snippet to this:
> >
> >     (defun ninrod--protection (buffer-assassin buffer-to-kill &rest
> > arguments)
> >       (if (equal buffer-to-kill "*scratch*")
> >           (message "DENIED! don't kill my precious *scratch*!!")
> >         (apply buffer-assassin arguments)))
> >     (defun ninrod/scratch-bodyguard (buffer-assassin &rest arguments)
> >       (let ((buffer-to-kill (buffer-name (current-buffer))))
> >         (ninrod--protection 'buffer-assassin buffer-to-kill arguments)))
> >     (defun ninrod/scratch-protection (buffer-assassin &rest arguments)
> >       (let ((buffer-to-kill (car arguments)))
> >         (ninrod--protection 'buffer-assassin buffer-to-kill arguments)))
> >     (advice-add #'kill-this-buffer :around #'ninrod/scratch-bodyguard)
> >     (advice-add #'kill-buffer :around #'ninrod/scratch-protection)
>
> You should not quote 'buffer-assassin'. And when you pass '&rest
> arguments' to 'ninrod/scratch-protection', you should use
> 'apply'. Something like the following works from here.
>
>   (defun ninrod/scratch-bodyguard (buffer-assassin &rest arguments)
>     (let ((buffer-to-kill (buffer-name (current-buffer))))
>       (apply #'ninrod--protection buffer-assassin buffer-to-kill
> arguments)))
>
>   (advice-add #'kill-this-buffer :around #'ninrod/scratch-bodyguard)
>
> > This causes all hell to break loose. Now I can't even close emacs,
> because
> > apparently emacs tries to kill all buffers
> > and as I've just tampered with the kill buffer functions, well, it's bad.
> > Very bad.
> >
> > I know I mean well, but I'm must be doing something very stupid. For
> > starters, I don't know if I can really pass around
> > functions as parameters? So it could be that?
> >
> > How would you refactor that snippet to apply the dry principle?
> >
> > thanks in advance,
> >
> > Filipe.
>
>


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