merb widget

# lib/widgets/widget.rb
# Superclass for our form element "widgets"
class Widget
  include Merb::GlobalHelpers
 
  # This is necessary to include Merb::GlobalHelpers
  class_inheritable_accessor :_default_builder
 
  # These are for convenience
  attr_accessor :params
  attr_accessor :session
 
  def initialize(params = {}, session = {})
    self.params = params
    self.session = session
  end
 
  def value
  end
end
 
# lib/widgets/weight_input_switcher.rb
class WeightInputSwitcher < Widget
  attr_accessor :attribute_name, :weight_in_kg, :unit_preference
 
  # View methods
  def setup(attribute_name, weight_in_kg = nil, unit_preference = session[:unit_preference])
    self.attribute_name = attribute_name
    self.weight_in_kg = weight_in_kg
    self.unit_preference = unit_preference
    self
  end
 
  def switcher
    html = "<div class='weight_input_switcher'>"
    html += weight_input("lbs")
    html += weight_input("kg")
    html += weight_input("st")
    html += "</div>"
    html
  end
 
  def weight_input
    html = "<span class='weight_input #{unit_preference}'>"
    html += weight_input_field
    html += "</span>"
  end
 
  def weight_input_field
    if unit_preference == "st"
      stone, lbs = if weight_in_kg.to_i == 0
        ["",""]
      else
        weight_input_value(weight_in_kg, unit_preference).split(" st ")
      end
 
      html = text_field attribute_name, :value => stone, :name => "weight_input[stone]", :class => "weight_input_field stone"
      html += "<span class='weight_unit'>stone</span>"
      html += text_field attribute_name, :value => lbs, :name => "weight_input[lbs]", :class => "weight_input_field stone lbs"
      html += "<span class='weight_unit'>lbs</span>"
    else
      value = weight_input_value(weight_in_kg, unit_preference)
 
      html = text_field attribute_name, :value => value, :name => "weight_input", :class => "weight_input_field"
      html += "<span class='weight_unit'>" + unit_preference.to_s + "</span>"
    end
    html
  end
 
  # Parse methods
  # We kinda cheat here and use params. Need to figure out a better way to do this.
  def value
    if params["weight_input"]["stone"]
      "#{params["weight_input"]["stone"]} st #{params["weight_input"]["lbs"]} lbs"
    else
      "#{params["weight_input"]} #{Units.weight_full_to_abbreviation_map[unit_preference]}"
    end
  end
 
  private
  def weight_input_value(weight_in_kg, unit_preference)
    begin
      weight_in_kg.to_display_weight_without_unit(unit_preference)
    rescue
      ""
    end
  end
end
 
# The following is added to global_helpers.rb
def widget(klass, *args)
  klass.new(params, session).setup(*args)
end
 
# An example of using the "Widget" to display form elements
widget(WeightInputSwitcher, :weight, @current_user.current_weight).switcher
 
# An example of using the "Widget" to get the value of form elements
weight_widget = widget(WeightInputSwitcher, :weight, 0, "", user[:unit_preference])
weight = weight_widget.value