How to mapping from the value of one alist entry to the value of another entry of the same alist

Question

I have a data structure like: ((fid . FID) (name . NAME) (count . COUNT) (data . ORIGINAL_DATA))

I have following Elisp code try to interactively select FID through display the NAME instead of FID.

(defun emms-bilibili-favlist-select ()
  "Interactive select which favlist to open."
  (let* ((fav-name (completing-read "Select favlist: "
                                    (mapcar
                                     (lambda (x) (alist-get 'name x))
                                     (emms-bilibili--retrieve-favfolder))))
         ;; TODO:
         (favlist ...)
         )
    (emms-bilibili--retrieve-favlist (alist-get 'fid favlist))))

I need it to display a list in interactive select:

NAME A NAME B NAME C When I select "NAME A", code need to get the corresponding FID. (upper code is just my pseudo code, if you have better solution, please tell me, Thanks.)

Answer 1

If you can ensure names are unique, you can lookup the list of alist through NAME to get the corresponding FID, for example,

(let* ((alists
        '(((fid . 1) (name . "Name A"))
          ((fid . 2) (name . "Name B"))
          ((fid . 3) (name . "Name C"))))
       (name
        (completing-read
         "> "
         (mapcar
          (lambda (al) (alist-get 'name al))
          alists)))
       (alist
        (seq-find
         (lambda (al)
           (string= name (alist-get 'name al)))
         alists)))
  (alist-get 'fid alist))