Calling a function with a boolean return value inside of a trigger in postgres

Question

I am trying to call a function inside of a trigger in postgres. Basically I have a function,

c.check_level(bigint, integer)

which returns a boolean value.

I would like to call this function inside of a trigger as follows:

CREATE OR REPLACE FUNCTION c.check_level_tg()
RETURNS trigger AS
$BODY$
DECLARE
    parent_id  int8;
    level int;
    result bool;
begin
    parent_id := NEW.fk_parent;
    level := NEW.level;

    select * from c.check_category_level(parent_id, level) as result;

    if (result) then
        return (NEW);
    else 
        return(NULL);
    end if;

END; 
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
ALTER FUNCTION c.check_category_level_tg()
  OWNER TO postgres;

When I try to put data in the table on which this trigger resides, I get an error: "ERROR: query has no destination for result data HINT: If you want to discard the results of a SELECT, use PERFORM instead. CONTEXT: PL/pgSQL function".

The function c.check_level works properly when run in isolation.

Answer 1

Change

select * from c.check_category_level(parent_id, level) as result;

into:

SELECT c.check_category_level(parent_id, level) INTO result;