[Nix-dev] Nix language: converting an attribute set to a list
Cameron Turner
cam.turn at gmail.com
Mon Apr 14 11:13:10 CEST 2014
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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