# Loan Application Model
class LoanApplication < ActiveRecord::Base
  has_many :loan_securities, :dependent => :destroy
  accepts_nested_attributes_for :loan_securities, :allow_destroy => true
end

# Loan Security Model
class LoanSecurity < ActiveRecord::Base
  has_one :security_type
  accepts_nested_attributes_for :security_type
end

# Security Type Model
class SecurityType < ActiveRecord::Base
  belongs_to :loan_security
end

<%= nested_form_for [@business, @loanapplication], method: :put, :class => "form-horizontal", url: wizard_path, :html => { :multipart => true } do |f| %>
    <%= f.fields_for :loan_securities, :wrapper => true do |loan_security| %>
        <%= loan_security.collection_select(:security_type_id, SecurityType.all, :id, :name) %>
    <% end %>
<% end %>

loan_securities_attributes: [:id, :_destroy, security_type_attributes: [:security_type_id, :name]]