Problem saving associated models

Rails
1

I want to save data from User(parent model) when creating/editing a Shop
(child model).

My models:

    class User < ActiveRecord::Base
      has_one :shop, :dependent => :destroy
    end

    class Shop < ActiveRecord::Base
      belongs_to :user
      accepts_nested_attributes_for :user #!!!!!!!!!!!!
    end

My Shop controller:

    class ShopsController < ApplicationController
        def new
            @shop = Shop.new
            #@shop.user = current_user
            @shop.build_user
        end
    end

    def create
        @shop = Shop.new(params[:shop])

        @shop.user = current_user
        respond_to do |format|
        if @shop.save
            flash[:notice] = t(:shop_created)
            format.html { redirect_to(@shop) }
            format.xml { render :xml => @shop, :status => :created,
:location => @shop }
        else
            format.html { render :action => "new" }
            format.xml { render :xml => @shop.errors, :status =>
:unprocessable_entity }
        end
     end

    end

Shop page:

    <% form_for @shop, :html => {:multipart => true} do |f| %>
        <%- f.fields_for :user do |user| %>
            <%= user.text_field :name, :live => true %>
        <% end -%>
    <% end -%>

All examples that I found about saving associated models are when saving
from User (parent) N children ( my Shop model). In those cases I
understand where define accepts_nested_attributes_for.

My case is inverse.

Q: How can I save User data when submitting on Shop form ?