confusion about accepts_nested_attributes_for - ruby-on-rails

Question

Somehow, I was under impression that accepts_nested_attributes_for will let me populate child object through parent:
person.update_attributes person_hash
but in practice I ended up doing this:
person.address.update_attributes person_hash[:address]
person_hash.delete :address
person.update_attributes person_hash
Now, http://guides.rubyonrails.org mentions accepts_nested_attributes_for only indirectly and API documentation for this method is also quite cryptic.
1) Could someone show basic use-case for accepts_nested_attributes_for? I mean, I understand how it's declared, I'm confused about the difference it makes.
2) Is the way I populate nested object the 'right' one in rails, or there's something more 'elegant'?
Thanks!
update
Model, for clarity
class Person < ActiveRecord::Base
has_one :address
accepts_nested_attributes_for :address
end
update2, for j.
Form declaration goes like this
<% fields_for "people", person, :index => person.id do |person_form| %>
...
<% person_form.fields_for person.address do |address_form| %>
<%= address_form.text_field :street %>
<% end %>
...
<% end %>
But it gives me html names like people[66][address][street] and not people[66][address_attributes][street]

Answer 1

With accepts_nested_attributes_for you can do the following:
# example from railsapi.com
# view
<% form_for #person, :url => { :action => "create" } do |person_form| %>
Name: <%= person_form.text_field :name %>
...
<% person_form.fields_for :address do |address_fields| %>
Street : <%= address_fields.text_field :street %>
Zip code: <%= address_fields.text_field :zip_code %>
<% end %>
<% end %>
With this, your parameters will look like
params = {
:person => {
:name => 'Jack',
:address_attributes => { :street => 'Street', :zip_code => '11111' }
}
}
and you're able to create a person and the related address just using
#person = Person.create(params)
For more information, railsapi.com. I hope it helps.
Edit
I have no idea why your params look like this :/
But using
#person.address.update_attributes person_hash.delete(:address) OR
person.address.update_attributes person_hash[:address]
person_hash.delete :address
person.update_attributes person_hash
is not wrong. Just could be done with more elegant code, as you said.