Ruby on Rails

CUSTOMER MODEL:

class Customer < ActiveRecord::Base
   belongs_to :sender, :class_name => "Customer"
 has_many :receivers, :class_name => "Customer", :foreign_key => 'sender_id'
   has_many :packages 

accepts_nested_attributes_for :packages
accepts_nested_attributes_for :receivers
 end

CUSTOMER ADMIN INTERFACE:

ActiveAdmin.register Customer do
   form do |f|
 f.inputs "Sender Details" do
      f.input :name
 f.input :email
  f.input :street
 f.input :city
  f.input :state
 f.input :pin
   end

  f.inputs  do
f.has_many :receivers do |p|
    f.input :name
 f.input :email
  f.input :street
 f.input :city
  f.input :state
 f.input :pin
   end
end
f.inputs do #packages are saving correctly
  f.has_many :packages do |p| 
   p.input :weight
  p.input :amount
   p.input :received_date
  p.input :amount
 end
  end
  f.buttons
 end
 end