之前的 Erlang 语法错误：'end'

Question

我最近开始学习erlang，但是遇到了一个让我很困惑的错误。

最后一行的错误是syntax error before: 'end'。我查看了示例并试图找到错误，但此刻我完全迷失了。有什么想法吗？

ChannelToJoin = list:keysearch(ChannelName,1,State#server_st.channels),
case ChannelToJoin of
    % Channel exists.
    {value, Tuple} ->
        if 
            %User is not a member of the channel
            not list:member(UserID, Tuple) ->
            %Add the user to the channel
            Tuple#channel.users = list:append(Tuple#channel.users, [UserID]);


            % If the user is already a member of the channel.
            true -> true
        end;
    %Channel doesn't exist
    false ->
        %Create new channel and add the user to it.
        NewState = State#server_st{channels = list:append(State#server_st.channels, NewChannel = #channel{name = ChannelName, users = [UserID]}
end

Answer 1

倒数第二行 NewState = ... 缺少两个右括号：)}

还请注意，您不能在if 中使用lists:member，因为在保护表达式中不允许函数调用（这是if 允许您使用的）。相反，请使用case:

case lists:member(UserID, Tuple#channel.users) of
    false ->
         %% Add the user to the channel
         ...;
    true ->
         %% Already a member
         ok
end