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Versions: 5
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Contents
module Alf
module Engine
#
# Replace missing attributes and nil by default, computed values.
#
# Example:
#
# rel = [
# {:id => 1, :name => "Jones"},
# {:id => 2, :name => nil}
# ]
# Defaults.new(rel, TupleComputation[:name => "Smith"]).to_a
# # => [
# # {:id => 1, :name => "Jones"},
# # {:id => 2, :name => "Smith"}
# # ]
#
class Defaults < Cog
# @return [Enumerable] The operand
attr_reader :operand
# @return [TupleComputation] The default values
attr_reader :defaults
# Creates a Defaults instance
def initialize(operand, defaults)
@operand = operand
@defaults = defaults
end
# (see Cog#each)
def each
handle = Tools::TupleHandle.new
operand.each do |tuple|
defs = @defaults.evaluate(handle.set(tuple))
yield tuple.merge(defs){|k,v1,v2| (v1.nil? ? v2 : v1)}
end
end
end # class Defaults
end # module Engine
end # module Alf
Version data entries
5 entries across 5 versions & 1 rubygems