form_for tag and :id symbol issue


I am new to RoR and practice some ruby/rails language feathers on my
toy application. Here is a question about form_for tag in rails.

== the story
People profile can be modified by end user, so there is method called
"update_profile" in the controller.

== the view

<% form_for :person,@person, :url => |f|%>
    <%f.hidden_field :id %>
    <%f.text_field :ppl_name%>
<% end%>

== the controller
def update_profile
  person =[:person])

  person.new_record = false;

When I print out, the value is nil. However, i can set the
id using below code = params[:ppl_id]
Can someone explain why so weird? Thanks


I think if you are using form_for you need to use update_attributes()
to update the record

You don't want to create a new Person, do you? You want to just find
the existing person and update it:

person = Person.find(params[:id])

And also, new_record is generally something you don't want to touch -
rails will control it automatically.