Handling arrays in forms

I'm still working my way through Rails with the Thomas book. One
question is how to manage composition relationships in the view.
Suppose I have an polygon that is defined via a set of points express
as (x,y) paris. I have a table called polygons, and one called points,
with appropriate has_many relationships at the model and DB levels. I
want to enable the user to enter the polygon coordinates (multiple x,y
pairs) on the page - is there a standard way of doing this?

many thanks.