Pass a SELECT result as an argument to postgreSQL function

Question

I have a table "UserState" with following fields: id, userid, ctime, state, endtime. I have a simple query:

SELECT userid FROM "UserState" WHERE ctime>'2014-07-14'::timestamp

AND I have a plpgsql function, which must take the result of this query as an argument:

get_timeinstate(SELECT userid FROM "UserState" WHERE ctime>'2014-07-14'::timestamp);

How to create function correctly to pass a query result as parametr there? It's necessery to understand, that the function returns another SQL result and I need to use there "IN" condition:

$func$
BEGIN
 RETURN QUERY
 SELECT 
...myanotherquery...
 WHERE "UserState".userid IN (HERE I NEED TO INSERT MY QUERY RESULT)
END;
$func$

Answer 1

Pass the returned user_id set as array. Create the function to accept an integer array

create function get_timeinstate (
    user_id_set integer[],
    another_param...

Then call it passing the array generated by array_agg

get_timeinstate(
    (
        select array_agg(userid)
        from "UserState"
        where ctime>'2014-07-14'::timestamp
    ),
    another_param
);

Inside the function:

where "UserState".userid = any (user_id_set)

BTW if you are using plpgsql you can place the query inside the function and pass just the date:

create function get_timeinstate (
    p_ctime timestamp,
    another_param...
$func$
declare
    user_id_set integer[] := (
        select array_agg(userid)
        from "UserState"
        where ctime > p_ctime
    );
begin
    return query
    select 
    ...myanotherquery...
    where "UserState".userid = any (user_id_set)
end;
$func$