Re: Rebind key and save/reuse previous bound function

[Joe Riel <joer@san.rr.com>]

On Sat, 31 Oct 2015 13:22:29 -0700
John Mastro <john.b.mastro@gmail.com> wrote:

> Joe Riel <joer@san.rr.com> wrote:
> >
> > Is there a clean way save the function bound to a key
> > so that a new function can be created that is bound
> > to the same key, does something, then executes the
> > original bound function?
> 
> I don't think there's anything built-in that does exactly what you
> describe, but there are a few alternatives for doing it and all are
> pretty simple.
> 
> Something like this would probably be the most direct translation of
> your description:
> 
>     (defun define-before (map key cmd)
>       (let ((old (lookup-key map key)))
>         (define-key map key
>           (if (null old)
>               cmd
>             (lambda ()
>               (interactive)
>               (call-interactively cmd)
>               (call-interactively old))))))
> 
>     (define-before global-map (kbd "C-n")
>       (lambda ()
>         (interactive)
>         (message "Going to the next line!")))
> 
> However, I think using "before advice" is a nicer solution for this,
> because it integrates well with `describe-function'.
> 
>     (defun my-next-line-advice (&rest args)
>       (message "Going to the next line!"))
> 
>     (advice-add 'next-line :before #'my-next-line-advice)
> 
> The arguments your advice function receives will be the same as those
> for the original function you're advicing, if any. Check the
> documentation for `add-function' for a description of all the different
> kinds of advice and what arguments the advicing function receives.

Thanks.  Another user also suggested using advice.
I followed that advice 8-).



-- 
Joe Riel