select from composite type

Hello guys,
I'm trying to find out the equivalent behaviour of unnest, when I've got
just a composite type.

This is the statement is something like that (but more complex):

_sqlUpdate text=$$
with s as (
select * from ($1)
)
update myView as q set
(attribute_fullname, modify_user_id)
=(s.attribute_fullname, $2)
where s.product_code=q.product_code
and s.attribute_uid=q.attribute_uid
$$;

And I use this command.
execute _sqlUpdate using attribute_list[_i], _modify_user_id;

attribute_list is an array of composite type (with 20 fields).

If I use the unnest with the entire array the sql works, but I can't find a
way to treat the single record as a row of a table.

Any suggestions?

Bye and thanks'

Domenico