module Fiona7
  # Extracts widget object IDs from a widgetlist attribute read from
  # Fiona7::WriteObj#attr_values[]
  # 
  # The array contains integer IDs of the objects representing
  # the widgets within given attr_value.
  # For nil values it returns an empty array.
  class WidgetObjectIdCollector
    def initialize(attr_value)
      self.attr_value = attr_value
    end

    def call
      (attr_value || []).map do |widget_hash|
        widget_hash["destination"].try(:to_i)
      end.compact
    end

    protected
    attr_accessor :attr_value
  end
end