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Contents
require 'facets/functor'
module Enumerable
# Accumulate a set of a set. For example, in an ORM design
# where `Group has_many User` we might have something
# equivalent to the following.
#
# Group = Struct.new(:users)
# User = Struct.new(:name, :friends)
#
# user1 = User.new('John', [])
# user2 = User.new('Jane', ['Jill'])
# user3 = User.new('Joe' , ['Jack', 'Jim'])
#
# group1 = Group.new([user1, user2])
# group2 = Group.new([user2, user3])
#
# groups = [group1, group2]
#
# Now we can *accumulate* the users of all groups.
#
# groups.accumulate.users #=> [user1, user2, user3]
#
# You may pass an argument to perform chains, e.g. the following
# returns the names of users from all groups.
#
# groups.accumulate(2).users.name #=> ['John','Jane','Joe']
#
# Or we can gather all the friends of all users in groups.
#
# groups.accumulate(2).users.friends #=> ['Jill','Jack','Jim']
#
# This is more convenient then the equivalent.
#
# groups.accumulate.users.accumulate.friends #=> ['Jill','Jack','Jim']
#
# CREDIT: George Moshchovitis, Daniel Emirikol
def accumulate(iterations=1)
return self if iterations == 0
Functor.new do |op, *args|
result = inject([]) { |a, x| a << x.send(op, *args) }.flatten.uniq
result.accumulate(iterations - 1)
end
end
# Same as #accumulate, but does not apply #uniq to final result.
#
# groups.accumulate_all(2).users.friends #=> ['Jill', 'Jill','Jack','Jim']
#
def accumulate_all(iterations=1)
return self if iterations == 0
Functor.new do |op, *args|
result = inject([]) { |a, x| a << x.send(op, *args) }.flatten
result.accumulate_all(iterations - 1)
end
end
end
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