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# by Greg Houston # http://ghouston.blogspot.com/ require 'test/unit' class Test_Hash < Test::Unit::TestCase def test_hash_clones_string_key # demonstrates the behavior of Ruby's Hash # # when Ruby's Hash gets a String for a key, it appears to create a # new String with the same contents to use as the original string. # # unfortunately any overridden methods in the original string's singleton_class # are lost to the Hash key. h = Hash.new k = "key" class << k def foo; 'foo'; end end h[k] = "value" assert( k.respond_to?( :foo ), "k should have singleton_class method #foo" ) assert( !h.keys[0].respond_to?( :foo ), "key should not have singleton_class method #foo" ) ids = h.collect { |key,value| key.object_id } assert( !ids.include?( k.object_id ), "key in hash should have a different object_id" ) end end =begin >ruby try_hash_string_key.rb Loaded suite try_hash_string_key Started . Finished in 0.0 seconds. 1 tests, 3 assertions, 0 failures, 0 errors >Exit code: 0 =end

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