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box-o-sand/koans/about_open_classes.rb

46 lines
946 B

require File.expand_path(File.dirname(__FILE__) + '/edgecase')
class AboutOpenClasses < EdgeCase::Koan
class Dog
def bark
"WOOF"
end
end
def test_as_defined_dogs_do_bark
fido = Dog.new
assert_equal __, fido.bark
end
# ------------------------------------------------------------------
# Open the existing Dog class and add a new method.
class Dog
def wag
"HAPPY"
end
end
def test_after_reopening_dogs_can_both_wag_and_bark
fido = Dog.new
assert_equal __, fido.wag
assert_equal __, fido.bark
end
# ------------------------------------------------------------------
class ::Integer
def even?
(self % 2) == 0
end
end
def test_even_existing_built_in_classes_can_be_reopened
assert_equal __, 1.even?
assert_equal __, 2.even?
end
# NOTE: To understand why we need the :: before Integer, you need to
# become enlightened about scope.
end