bind/map a call to win_gotoid with script level argument

Question

I'm trying to set a nmap bind to make the focus change from Window B back to Window A. Both Window IDs are store at the script level: s:win_id_a and s:win_id_b.

The current snippet I've is the following at plugins/my-plugin.vim:

function! s:InitialSetup
  let s:win_id_a = win_getid()
  bot new
  let s:win_id_b = win_getid()
  " bunch of unrelated setups ...
  win_gotoid(s:win_id_b)  " Making sure we are binding the correct win/buff
  map <buffer> c :call win_gotoid(s:win_id_a)<CR>
endfunction

When I tried to trigger the map/bind I got an error: Undefined variable: s:win_id_a.

The question is: Should I "cast" s:win_id_ato a global OR is there another way I can achieve this win_gotoid bind call passing the script level variable?

Answer 1

The righthand side of a mapping is a series of key presses. That is, it works almost as if you pressed sequentially key "colon", then "c", then "a", then "l", etc.etc. on your keyboard.

Therefore, the righthand side of mapping is not a command and it can't have any script context associated with it. And therefore you can't access script-local variables within it.

Speaking of your case, use window-local variables to store data per window, or global variables when appropriate.

It is also possible to call script-local functions from mapping (and so to get access to script-local variables from inside). But in VimScript local functions are actually "globals" with mangled names, so they are accessible from everywhere, unlike variables.