gistfile1.rb

  validates_with_method :fecha_de_inicio, :method => :checa_es_dia_habil

  def checa_es_dia_habil(campo)
    if DiaInhabil.es_inhabil?(self.send(campo))
      return [false, "No es día hábil"]
    end
    true
  end


validates_with_method :fecha_de_inicio, :method => :checa_es_dia_habil, :pass_field => true

class DataMapper::Validate::MethodValidator
  def call(target)
    result,message = if @options[:pass_field]
      target.send(@options[:method], @field_name)
    else
      target.send(@options[:method])
    end
    add_error(target,message,@field_name) if !result
    result
  end
end


class DataMapper::Validate::MethodValidator
  def call(target)
    #"#{@options[:method]} => #{target.method(@options[:method]).arity}".tap
    result,message = if target.method(@options[:method]).arity > 0
      target.send(@options[:method], @field_name)
    else
      target.send(@options[:method])
    end
    add_error(target,message,@field_name) if !result
    result
  end
end