box-o-sand/koans/about_constants.rb

88 lines
2.0 KiB
Ruby

require File.expand_path(File.dirname(__FILE__) + '/edgecase')
C = "top level"
class AboutConstants < EdgeCase::Koan
C = "nested"
def test_nested_constants_may_also_be_referenced_with_relative_paths
assert_equal __, C
end
def test_top_level_constants_are_referenced_by_double_colons
assert_equal __, ::C
end
def test_nested_constants_are_referenced_by_their_complete_path
assert_equal __, AboutConstants::C
assert_equal __, ::AboutConstants::C
end
# ------------------------------------------------------------------
class Animal
LEGS = 4
def legs_in_animal
LEGS
end
class NestedAnimal
def legs_in_nested_animal
LEGS
end
end
end
def test_nested_classes_inherit_constants_from_enclosing_classes
assert_equal __, Animal::NestedAnimal.new.legs_in_nested_animal
end
# ------------------------------------------------------------------
class Reptile < Animal
def legs_in_reptile
LEGS
end
end
def test_subclasses_inherit_constants_from_parent_classes
assert_equal __, Reptile.new.legs_in_reptile
end
# ------------------------------------------------------------------
class MyAnimals
LEGS = 2
class Bird < Animal
def legs_in_bird
LEGS
end
end
end
def test_who_wins_with_both_nested_and_inherited_constants
assert_equal __, MyAnimals::Bird.new.legs_in_bird
end
# QUESTION: Which has precedence: The constant in the lexical scope,
# or the constant from the inheritance heirarachy?
# ------------------------------------------------------------------
class MyAnimals::Oyster < Animal
def legs_in_oyster
LEGS
end
end
def test_who_wins_with_explicit_scoping_on_class_definition
assert_equal __, MyAnimals::Oyster.new.legs_in_oyster
end
# QUESTION: Now Which has precedence: The constant in the lexical
# scope, or the constant from the inheritance heirarachy? Why is it
# different than the previous answer?
end