Contents

require 'forwardable'
require 'compo/composite'

module Compo
  # Null implementation of Composite
  #
  # Add/remove operations on NullComposite always fail, and #children always
  # returns the empty hash.
  #
  # This is useful for leaf classes that still need to expose the composite
  # API.
  class NullComposite
    include Composite

    # Returns the empty hash
    #
    # @api  public
    # @example  Gets the children
    #   comp.children
    #   #=> {}
    #
    # @return [Hash]  The empty hash.
    def children
      {}
    end

    private

    # Fails to add a child into the NullComposite
    #
    # @api  private
    #
    # @param id [Object]  Ignored.
    # @param child [Object]  Ignored.
    #
    # @return [nil]
    def add!(_, _)
      nil
    end

    # Fails to remove the given child
    #
    # @api  private
    #
    # @param child [Object]  Ignored.
    #
    # @return [nil]
    def remove!(_)
      nil
    end

    # Fails to remove the child with the given ID
    #
    # @api  private
    #
    # @param id [Object]  Ignored.
    #
    # @return [nil]
    def remove_id!(_)
      nil
    end
  end
end

Version data entries

5 entries across 5 versions & 1 rubygems

Version	Path
compo-0.1.4	lib/compo/null_composite.rb
compo-0.1.3	lib/compo/null_composite.rb
compo-0.1.2	lib/compo/null_composite.rb
compo-0.1.1	lib/compo/null_composite.rb
compo-0.1.0	lib/compo/null_composite.rb