如何在rails 3.1.0视图中设置只读字段？

class User < ActiveRecord::Base
  # ...
  def readonly?
    true
  end
end

<%= f.text_field :readonly, :readonly => true %>

class User < ActiveRecord::Base
  # ...
  def readonly?
    true
  end
end

class UsersController < ApplicationController
  # ...
  def update
    @user = User.find(params[:id])
    @user.update_attributes(params[:user])
    render json: { readonly: @user.readonly? }
  end
end