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Contents
module Enumerable
unless method_defined?(:group_by) # 1.9
# Enumerable#group_by is used to group items in a collection by something
# they have in common. The common factor is the key in the resulting hash,
# the array of like elements is the value.
#
# (1..5).group_by { |n| n % 3 }
# #=> { 0 => [3], 1 => [1, 4], 2 => [2,5] }
#
# Applied to an array.
#
# ["I had", 1, "dollar and", 50, "cents"].group_by { |e| e.class }
# #=> { String => ["I had","dollar and","cents"], Fixnum => [1,50] }
#
# Applied to a hash:
#
# {:a=>1, :b=>2, :c=>1}.group_by{ |k,v| v }
# #=> { 1=>[[:c,1], [:a,1]], 2=>[[:b,2]] }
#
# CREDIT: Erik Veenstra
def group_by #:yield:
r = Hash.new
each{ |e| (r[yield(e)] ||= []) << e }
r
end
end
end
Version data entries
7 entries across 6 versions & 1 rubygems