Checking and assigning a value within cond

Questions / Help
1

I have code like this:

    {rating_check_passed, rating_check_msg} =
      LobbyPolicy.check_rating_to_play(user.id, state)

    cond do
      not rating_check_passed ->

Is there a way to move the calling of the function check_rating_to_play inside the cond itself?

I tried this:

    cond do
      LobbyPolicy.check_rating_to_play(user.id, state) == {false, rating_check_msg} ->
      #I need to do something with rating_check_msg here

but that doesn’t work. The benefit of calling the function within the cond is that if I had some other checks within the cond that satisfy first the function doesn’t get called.

2

In these cases I usually prefer use case do:

case LobbyPolicy.check_rating_to_play(user.id, state) do
  {true, _msg} -> # ...
  {false, msg} -> # ...
end
3

Looks like code that can be further broken apart. If you show some more code we’ll help you but as @emadb said, case can be applied here. Or different variants of pattern-matching function heads.

4

If it helps for me to show more code, here’s what I have originally:

    {rating_check_passed, rating_check_msg} =
      LobbyPolicy.check_rating_to_play(user.id, state)

    {rank_check_passed, rank_check_msg} = LobbyPolicy.check_rank_to_play(user, state)

    cond do
      not rating_check_passed ->
        # Send message
        msg = rating_check_msg
        CacheUser.send_direct_message(get_coordinator_userid(), userid, msg)
        false

      not rank_check_passed ->
        # Send message
        msg = rank_check_msg
        CacheUser.send_direct_message(get_coordinator_userid(), userid, msg)
        false

      #some more stuff here

      true ->
        true
    end

Basically
LobbyPolicy.check_rating_to_play
LobbyPolicy.check_rank_to_play

are always called. But in theory it would be more efficient if it checks one, then if that passes call the other to see if that passes.

5

Now that sounds like a job for with.

2 Likes