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module Alf
module Engine
#
# Provides in-memory materialization through a ruby Array.
#
# This class acts as a Cog, that it, it is an enumerable of tuples. An
# optional ordering can be passed at construction.
#
# Materialization occurs at prepare time, with auto-prepare on first
# access.
#
# Example:
#
# rel = [
# {:name => "Jones", :city => "London"},
# {:name => "Smith", :city => "Paris"},
# {:name => "Blake", :city => "London"}
# ]
#
# Materialize::Array.new(rel).to_a
# # => same as rel, in same order as the source
#
# Materialize::Array.new(rel, Ordering[[:name, :asc]]).to_a
# # => [
# {:name => "Blake", :city => "London"},
# {:name => "Jones", :city => "London"},
# {:name => "Smith", :city => "Paris"}
# ]
#
class Materialize::Array < Cog
# @return [Enumerable] The operand
attr_reader :operand
# @return [Ordering] Ordering to ensure (optional)
attr_reader :ordering
# Creates a Materialize::Array instance
def initialize(operand, ordering = nil)
@operand = operand
@ordering = ordering
@materialized = nil
end
# (see Cog#each)
def each(&block)
materialized.each(&block)
end
# (see Cog#prepare)
#
# Prepare through materialization of the operand as an ordered array
def prepare
@materialized ||= begin
arr = operand.to_a
arr.sort!(&ordering.sorter) if ordering
arr
end
end
# (see Cog#free)
#
# Frees the materizalied hash
def clean
@materialized = nil
end
private
# @return [Array] the materialized array
def materialized
prepare
@materialized
end
end # class Materialize::Array
end # module Engine
end # module Alf
Version data entries
5 entries across 5 versions & 1 rubygems