Putting variable in regexp_substr pattern returns nothing

Question

I'm trying to create a function to simply extract positioned text from a string, ie I want the text in position two from string X with a pattern of ' - '. I want to create a function so it is simpler for the developers but regexp_substr doesn't seem to like it.
So I want a function like below to be executed, select text_extractor('ABC - DEF - HIJ',' - ',2) from dual; which would return DEF;
But regexp_substr doesn't like matching on ' - '. If I tell it to give me position 2, I get '-', and if I tell it position 3, I get DEF. It seems to work fine if the '-' is substritued with a ':'
ie
select regexp_substr('ABC - DEF - HIJ','[^ - ]+',1,2) from dual;
results
select regexp_substr('ABC - DEF - HIJ','[^ - ]+',1,3) from dual;
results
DEF
select regexp_substr('ABC : DEF : HIJ','[^ : ]+',1,2) from dual;
results
DEF
I would further like to make a function to wrap it in but it didn't work at all.
The following examples return nothing.
create or replace function text_extractor (p_text varchar2, p_delimiter varchar2, p_position number)
return varchar2
is
begin
return (regexp_substr(p_text,'^p_delimiter]+', 1,p_position));
end;
I've also tried
create or replace function text_extractor (p_text varchar2, p_delimiter varchar2, p_position number)
return varchar2
is
v_search_expression varchar2(2000);
begin
v_search_expression := '''[^'||p_delimiter||']+''';
return (regexp_substr(p_text,v_search_expression),1,p_position);
end;
But I get nothing. Any ideas?

Answer 1

When you do this:
select regexp_substr('ABC - DEF - HIJ','[^ - ]+',1,2) from dual;
results
-Your search string is a set of characters, so you are saying anything that is NOT a space or dash (or space again, but that's redundant). So the first match is ABC, the second match is "-" as that's the second non-space match, so that's why you get that. Probably what you want is to ignore the spaces and use the "-" as your delimiter, then just trim the spaces off after...
SQL> ed
Wrote file afiedt.buf
  1* select trim(regexp_substr('ABC - DEF - HIJ','[^-]+',1,2)) from dual
SQL> /
TRI
DEF
SQL>