dynamic date+time acessors a datetime attribute in rails model

controller.rb

# and you can handle formating in your controller
def action
  params[:start_at] = params[:start_at_date] + ' ' + params[:start_at_time]
  params.delete :start_at_date
  params.delete :start_at_time
end

form.rb

class Form
  class << self

    def add_acessors(obj, *attrs)
      attrs.each do |attr|
        obj.instance_eval "class << self; attr_accessor \"#{attr.to_s}\"; end;"
      end
    end

    def split_date_time(obj, attr)
      attr = attr.to_s
      date_attr = attr + '_date'
      time_attr = attr + '_time'

      add_acessors obj, date_attr, time_attr

      value = obj.send(attr)
      if value.respond_to?(:strftime)
        obj.send date_attr +'=', value.strftime('%d/%m/%Y')
        obj.send time_attr +'=', value.strftime('%H:%M')
      end
    end
  end
end

view.html.haml

- Form.split_date_time resource, :start_at          
= f.input :start_at_date, :as => :date_picker
= f.input :start_at_time, :as => :time_text

Sick of writing accessors and poluting yout model class?

oh, it is a big shame to use model for form binding (i.e. no command or dto) -> that's the rails way :p