在 Erlang 中处理复杂的列表

Question

我在 Erlang 中有这个列表

[{title,
"ad"},
{description,
"fdf"},
{allow_change_subj,
true},
{allow_query_users,
true},
{allow_private_messages,
true},
{allow_private_messages_from_visitors,
anyone},
{allow_visitor_status,
true},
{allow_visitor_nickchange,
true},
{public,
true},
{public_list,
true},
{persistent,
true},
{moderated,
true},
{members_by_default,
true},
{members_only,
false},
{allow_user_invites,
true},
{password_protected,
false},
{captcha_protected,
false},
{password,
[]},
{anonymous,
true},
{logging,
false},
{max_users,
200},
{allow_voice_requests,
true},
{voice_request_min_interval,
1800},
[{captcha_whitelist, []}, 
{affiliations, [{{"test1", "serverdomain.com", []},{owner,[]}}]}, {{"testuser4_gmail.com", "serverdomain.com", []},    {member, []}}],
{subject,
[]},
{subject_author,
[]}]]

我正在尝试获取密钥 'affiliations' 下的用户名 (test1, testuser4_gmail.com)，但无法从此列表中获取它们。

如有任何帮助，我们将不胜感激。

更新：

我很高兴获得 'affilations' 密钥及其下的所有内容，但我正在寻找的问题。我举个例子

 ->   Listt = [{captcha_whitelist, []}, {affiliations, [{{"test1", "54.69.16.10", []},{owner,[]}}]}].
    
  ->  lists:keyfind('affiliations',1, Listt).
  Output : {affiliations,[{{"test1","54.69.16.10",[]},{owner,[]}}]}

Target : 获取像“test1”这样的值，如果那里有更多的值，比如“test1”，“testuser4_gmail.com”

Answer 1

根据您的代码示例，您可以通过以下方式进一步提取。

这是您的代码示例结构：

1> Listt = [{captcha_whitelist, []}, {affiliations, [{{"test1", "54.69.16.10", []},{owner,[]}}]}].
[{captcha_whitelist,[]},
 {affiliations,[{{"test1","54.69.16.10",[]},{owner,[]}}]}]

我会用 proplists 提取第一层：

2> Affiliations =  proplists:get_value(affiliations,Listt).
[{{"test1","54.69.16.10",[]},{owner,[]}}]

lists:map/2 和模式匹配可以帮助您仅使用结构的第一部分来转换列表：

3> Users = lists:map(fun({User, Role}) -> User end, Affiliations).
[{"test1","54.69.16.10",[]}]

如果你想进一步提取，你可以这样做：

4> lists:map(fun({Username, Server, _}) -> Username end, User). 
["test1"]

或者您甚至可以同时执行第 3 步和第 4 步并获取用户列表：

5> lists:map(fun({{User, Server, _}, Role}) -> User end, Affiliations).       
["test1"]

在 Erlang 中处理复杂的列表

Manipulating complex lists in Erlang

erlang

ejabberd