mnesia - Erlang check empty string -

mnesia - Erlang check empty string -

i'm new in erlang development. i'm trying read value of accesstoken mnesia table (stored in 'users' table).

in code i've done:

buser = boss_db:find(users, [{email, 'equals', myemail}]), [{_,_,bemail,bname,bpassword,_,baccesstoken}] = buser, io:format("user details ~n~p~n", [buser]), io:format("access token ~n~p~n", [baccesstoken]), . .

i get:

user details [{users,"users-1","mymail@someemail.org","some name","somepassword",'',''}]

the lastly field accesstoken , printed as:

access token ''

if accesstoken value non empty i'll operation.

how check if accesstoken empty or not?

i tried:

accesstokenlength = length(baccesstoken) if accesstokenlength > 0 -> . .

but next error:

error in controller error badarg [{erlang,length,[''],[]}

i tried:

case binary_to_list(baccesstoken) =/= [] of true-> false->

but next error:

error in controller error badarg [{erlang,binary_to_list,[''],[]}

how check empty status properly?

you pattern match on value

case baccesstoken of '' -> %% empty _ -> %% not empty end

and 1 more thing. single quotes in erlang signifies atom. can write starting lover case letter, atom or false or not_empty. utilize more "complex" atom utilize single quote 'this atom'. , '' "empty atom.

and empty binary <<>>.

erlang mnesia