# iterator.rb
# Provides a way to access the elements of an aggregate object sequentially without exposing
# its underlying representation.
# 1. external iteator
class ExternalIterator
def initialize(array)
@array = Array.new(array)
@index = 0
end
def has_next?
@index < @array.length
end
def next
value = @array[@index]
@index += 1
value
end
def current_element
@array[@index]
end
end
# 2. internal iteator
module InternalIterator
def initialize()
@array = []
end
def each()
copy = Array.new(@array)
i = 0
while i < copy.length
if block_given?
yield(copy[i])
end
i += 1
end
end
end
class TestInternalIterator
include InternalIterator
def initialize
super
@array = ['i1', 'i2', 'i3', 'i4']
end
end
# 3. Iterator with help of Enumerable
class Element
attr_accessor :name, :value
def initialize(name, value)
@name = name
@value = value
end
# this method is important for Enumerable
def <=>(other)
value <=> other.value
end
end
class TestEnumerable
include Enumerable
def initialize
@array = []
end
def each(&block)
@array.each(&block)
end
def <<(element)
@array << element
end
end
# test
array = ['e1', 'e2', 'e3', 'e4']
e_it = ExternalIterator.new(array)
while e_it.has_next?
puts e_it.next.to_s
end
i_it = TestInternalIterator.new()
i_it.each {|e| puts e.to_s}
test = TestEnumerable.new
el = Element.new("n2", 2001)
test << Element.new("n1", 1)
test << el
test << Element.new("n3", 22)
test << Element.new("n4", 64)
puts "Has n2: " + test.include?(el).to_s
puts "All elements have value >= 10: " + (test.all? {|e| e.value >= 10}).to_s
puts "Has any element with value >= 2000: " + (test.any? {|e| e.value > 2000}).to_s
