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require File.expand_path(File.dirname(__FILE__) + '/edgecase')
class AboutMessagePassing < EdgeCase::Koan
class MessageCatcher
def caught?
true
end
end
def test_methods_can_be_called_directly
mc = MessageCatcher.new
assert mc.caught?
end
def test_methods_can_be_invoked_by_sending_the_message
mc = MessageCatcher.new
assert mc.send(:caught?)
end
def test_methods_can_be_invoked_more_dynamically
mc = MessageCatcher.new
assert mc.send("caught?")
assert mc.send("caught" + "?" ) # What do you need to add to the first string?
assert mc.send("CAUGHT?".downcase ) # What would you need to do to the string?
end
def test_send_with_underscores_will_also_send_messages
mc = MessageCatcher.new
assert_equal true, mc.__send__(:caught?)
# THINK ABOUT IT:
#
# Why does Ruby provide both send and __send__ ?
end
def test_classes_can_be_asked_if_they_know_how_to_respond
mc = MessageCatcher.new
assert_equal true, mc.respond_to?(:caught?)
assert_equal false, mc.respond_to?(:does_not_exist)
end
# ------------------------------------------------------------------
class MessageCatcher
def add_a_payload(*args)
args
end
end
def test_sending_a_message_with_arguments
mc = MessageCatcher.new
assert_equal [], mc.add_a_payload
assert_equal [], mc.send(:add_a_payload)
assert_equal [3,4,nil,6], mc.add_a_payload(3, 4, nil, 6)
assert_equal [3,4,nil,6], mc.send(:add_a_payload, 3, 4, nil, 6)
end
# ------------------------------------------------------------------
class TypicalObject
end
def test_sending_undefined_messages_to_a_typical_object_results_in_errors
typical = TypicalObject.new
exception = assert_raise(NoMethodError) do
typical.foobar
end
assert_match(/foobar/, exception.message)
end
def test_calling_method_missing_causes_the_no_method_error
typical = TypicalObject.new
exception = assert_raise(NoMethodError) do
typical.method_missing(:foobar)
end
assert_match(/foobar/, exception.message)
# THINK ABOUT IT:
#
# If the method :method_missing causes the NoMethodError, then
# what would happen if we redefine method_missing?
#
# NOTE:
#
# In Ruby 1.8 the method_missing method is public and can be
# called as shown above. However, in Ruby 1.9 the method_missing
# method is private. We explicitly made it public in the testing
# framework so this example works in both versions of Ruby. Just
# keep in mind you can't call method_missing like that in Ruby
# 1.9. normally.
#
# Thanks. We now return you to your regularly schedule Ruby
# Koans.
end
# ------------------------------------------------------------------
class AllMessageCatcher
def method_missing(method_name, *args, &block)
"Someone called #{method_name} with <#{args.join(", ")}>"
end
end
def test_all_messages_are_caught
catcher = AllMessageCatcher.new
assert_equal "Someone called foobar with <>", catcher.foobar
assert_equal "Someone called foobaz with <1>", catcher.foobaz(1)
assert_equal "Someone called sum with <1, 2, 3, 4, 5, 6>", catcher.sum(1,2,3,4,5,6)
end
def test_catching_messages_makes_respond_to_lie
catcher = AllMessageCatcher.new
assert_nothing_raised(NoMethodError) do
catcher.any_method
end
assert_equal false, catcher.respond_to?(:any_method)
end
# ------------------------------------------------------------------
class WellBehavedFooCatcher
def method_missing(method_name, *args, &block)
if method_name.to_s[0,3] == "foo"
"Foo to you too"
else
super(method_name, *args, &block)
end
end
end
def test_foo_method_are_caught
catcher = WellBehavedFooCatcher.new
assert_equal "Foo to you too", catcher.foo_bar
assert_equal "Foo to you too", catcher.foo_baz
end
def test_non_foo_messages_are_treated_normally
catcher = WellBehavedFooCatcher.new
assert_raise(NoMethodError) do
catcher.normal_undefined_method
end
end
# ------------------------------------------------------------------
# (note: just reopening class from above)
class WellBehavedFooCatcher
def respond_to?(method_name)
if method_name.to_s[0,3] == "foo"
true
else
super(method_name)
end
end
end
def test_explicitly_implementing_respond_to_lets_objects_tell_the_truth
catcher = WellBehavedFooCatcher.new
assert_equal true, catcher.respond_to?(:foo_bar)
assert_equal false, catcher.respond_to?(:something_else)
end
end