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Erlang: simple refactoring

Consider the code:

f(command1, UserId) ->
    case is_registered(UserId) of
        true ->
            %% do command1
            ok;
        false ->
            not_registered
    end;

f(command2, UserId) ->
    case is_registered(UserId) of
        true ->
            %% do command2
            ok;
        false ->
            not_registered
    end.

is_registered(UserId) ->
    %% some checks

Now imagine that there are many commands, and all of them are first called is_registered . Is there a way to generalize this behavior (reorganize this code)? I mean, in all teams it is not recommended to place the same case .

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5 answers

I would go with

f(Command, UserId) ->
    case is_registered(UserId) of
         true  ->
             run_command(Command);
         false ->
             not_registered
    end.


run_command(command1) -> ok;   % do command1
run_command(command2) -> ok.   % do command2
+7
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I think the ctulahoops code is better reorganized like this:

run_command(Command, UserId) ->
    case is_registered(UserId) of
         true  ->
             Command();
         false ->
             not_registered
    end.

run_command(some_function_you_define);
run_command(some_other_function_you_define);
run_command(fun() -> do_some_ad_hoc_thing_here end).

, Erlang. , . -. cthulahoops , run_command(), .

+5
f(Command, UserId) ->
     Registered = is_registered(UserID),   
     case {Command, Registered} of
          {_, False} ->
               not_registered;
          {command1, True} ->
               %% do command1
               ok;
          {command2, True} ->
               %% do command2
               ok
     end.

is_registered(UserId) ->
     %% some checks

Wrangler, , .

+2

. , .

+1

, :

f(Command, UserId) ->
    f(Command,is_registered(UserId),UserID).

f(command1,true,_UserID) -> do_command1();
% if command2 does not need to be registered but uses UserID, for registration for example
f(command2,_Reg,UserID) -> do_command2(User_ID);
f(_,false,_UserID) -> {error, not_registered}.
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