Interactively select multiple items

Question

How can I let the user select multiple items from a list instead of just one? Like in the C-x b menu in helm.

Currently I can only select a single item instead of getting a complete list:

(defun test-main ()
  (interactive)
  (let ((choice (completing-read "Select: " '("item1 item2 item3"))))
    (message choice)))

Answer 1

You can do that with completing-read-multiple:

(defun test-main ()
  (interactive)
  (let ((choice (completing-read-multiple "Select: " '("item1" "item2" "item3"))))
    (message "%S" choice)))

It returns the selected items as a list, so if you type item2,item3 at the prompt, it returns ("item2" "item3").

Answer 2

Because that's what vanilla completing-read does. It reads and returns a single choice, providing completion to help you choose.

You can do what you are asking for with Icicles. It redefines function completing-read when Icicle mode is on.

Many Icicles commands are multi-commands, which means that you can make multiple input choices in a single command execution: a multiple-choice command. You can define your own multi-commands, using any actions.

And for any completion (not just for a multi-command), you can manipulate, save, and restore sets of completion candidates.

(You can also enter multiple inputs in the minibuffer. This is useful even for commands that read input without completion.)