class ActionView::Helpers::Tags::CheckBox

def checked?(value)
  case value
  when TrueClass, FalseClass
    value == !!@checked_value
  when NilClass
    false
  when String
    value == @checked_value
  else
    if value.respond_to?(:include?)
      value.include?(@checked_value)
    else
      value.to_i == @checked_value.to_i
    end
  end
end

def hidden_field_for_checkbox(options)
  @unchecked_value ? tag("input", options.slice("name", "disabled", "form").merge!("type" => "hidden", "value" => @unchecked_value, "autocomplete" => "off")) : "".html_safe
end

def initialize(object_name, method_name, template_object, checked_value, unchecked_value, options)
  @checked_value   = checked_value
  @unchecked_value = unchecked_value
  super(object_name, method_name, template_object, options)
end

def render
  options = @options.stringify_keys
  options["type"]     = "checkbox"
  options["value"]    = @checked_value
  options["checked"] = "checked" if input_checked?(options)
  if options["multiple"]
    add_default_name_and_id_for_value(@checked_value, options)
    options.delete("multiple")
  else
    add_default_name_and_id(options)
  end
  include_hidden = options.delete("include_hidden") { true }
  checkbox = tag("input", options)
  if include_hidden
    hidden = hidden_field_for_checkbox(options)
    hidden + checkbox
  else
    checkbox
  end
end