class ReeMapper::FieldsFilter::OnlyStrategy

def allow?(field)
  fields.include? field
end

def initialize(only, except)
  @fields = Set.new
  only.each do |item|
    if item.is_a? Symbol
      @fields << item
    else
      item.each do |key, val|
        @fields << key
      end
    end
  end
  if !except.nil?
    except.each do |item|
      if item.is_a? Symbol
        @fields.delete item
      else
        item.each do |key, val|
          @fields.delete key
        end
      end
    end
  end
end