[Nix-dev] Nix language: converting an attribute set to a list

[Sergey Mironov]

Thanks, looks like I didn't notice this possibility! Works just how I expected.

Sergey

2014-04-14 13:13 GMT+04:00 Cameron Turner <cam.turn at gmail.com>:
> The implementation of this would be:
>
> users = {
>         root = { name = "root"; group = groups.root; };
>         ssh = { name = "ssh" ; group = groups.nogroup ; severity = 33; };
>       };
> userList = (map (key: getAttr key users) (attrNames users));
>
> Roughly based on some code in Disnix's lib.nix. I'm sure you could split this out into a library function (maybe that's already been done), but there's no need for it to be a built-in.
>
> Shell
>
> Sergey Mironov <grrwlf at gmail.com> wrote:
> Hi. Nix language has a built-in function builtins.listToAttrs which
> converts list to the Attrs. I'm searching a way to make an opposite
> thing - convert attrs to a list. Say, I'd like to convert
>
>       users = {
>         root = { name = "root"; group = groups.root; };
>         ssh = { name = "ssh" ; group = groups.nogroup ; severity = 33; };
>       };
>
> to a list like this:
>
>       [
>         { name = "root"; group = groups.root; }
>         { name = "ssh" ; group = groups.nogroup ; severity = 33; }
>       ];
>
> to use it later both in shell scripting, as list
>
> lib.map  (toList users) (u: ''
>   adduser ${u.name} ${u.group}
> '');
>
> .. and in derivations, by reference
>
> stdenv.mkDerivation "ssh" {
>   user = users.ssh;
> };
>
> In order to workaround the problem I have to add additional field
> `list' (like below) but this way I have to duplicate field names which
> is not good (easy to forget). So Is it possible to do the
> transformation in a more
> safe way?
>
> Regards,
> Sergey
>
> # A workaround
>
>       users = rec {
>         root = { name = "root"; group = groups.root; };
>         ssh = { name = "ssh" ; group = groups.nogroup ; severity = 33; };
>         list = [ root ssh ];
>       };
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