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require 'test/unit'
require 'facets/multiton'
#
# EXAMPLE A - STANDARD USAGE
#
class TC_Multiton_A < Test::Unit::TestCase
class SomeMultitonClass
include Multiton
attr :arg
def initialize(arg)
@arg = arg
end
end
def test_standard
a = SomeMultitonClass.instance(4)
b = SomeMultitonClass.instance(4) # a and b are same object
c = SomeMultitonClass.instance(2) # c is a different object
assert_equal( a, b )
assert_equal( 42, [a.arg,b.arg].max * 10 + c.arg )
end
end
#
# EXAMPLE B - MODIFY AN EXISTING CLASS, SHARED FILEHANDLES
#
class TC_Multiton_B < Test::Unit::TestCase
class ::File
include Multiton
end
def test_modify_existing
lineno = __LINE__
# HERE1
# HERE2
a = File.instance(__FILE__)
b = File.instance(__FILE__)
assert_equal( a, b )
lineno.times{ a.gets }
assert_equal( "# HERE1", a.gets.strip )
assert_equal( "# HERE2", b.gets.strip )
end
end
#
# EXAMPLE C - INHERITENCE
#
class TC_Multiton_C < Test::Unit::TestCase
class A < String
include Multiton
end
# B is also a multiton - with it's OWN object cache
class B < A; end
def test_inheritence
# w is the same object as x, y is the same object as z
w,x,y,z = A.instance('A'), A.instance('A'), B.instance('B'), B.instance('B')
assert_equal( w.object_id, x.object_id ) # -> true
assert_equal( y.object_id, z.object_id ) # -> true
a = B.instance('A')
b = B.instance('A')
assert_not_equal( a.object_id, w.object_id ) # -> false (each class has it's own pool)
assert_equal( a.object_id, b.object_id ) # -> true
end
end
#
# EXAMPLE D - MULTIPLE MODULE INCLUSION (does nothing)
#
class TC_Multiton_D < Test::Unit::TestCase
class A < String
include Multiton
end
# B is also a multiton - with it's OWN object cache
class B < A; end
def test_multiple
# w is the same object as x, y is the same object as z
w,x,y,z = A.instance('A'), A.instance('A'), B.instance('B'), B.instance('B')
yz_id = y.object_id || z.object_id
B.class_eval {
include Multiton
}
# y is not only the same object as z, but they are both the same object(s)
# as from EXAMPLE C
y,z = B.instance('B'), B.instance('B')
assert_equal( y.object_id, yz_id ) # -> true
assert_equal( z.object_id, yz_id ) # -> true
end
end
#
# EXAMPLE E - SO YOU WANNA USE NEW INSTEAD OF INSTANCE...
#
class TC_Multiton_E < Test::Unit::TestCase
module K
# use an inner class which is itself a multiton
class K < String; include Multiton; end
# define a new which returns a mutltion using #instance...
class << self
def new(*args, &block)
K.instance(*args, &block)
end
end
end
def test_new
the = K.new '4'
answer = K.new '2'
assert_equal( "42", sprintf( "%s%s", the, answer ) ) #-> 42
assert_equal( K::K, the.class ) #-> K::K
end
end
#
# EXAMPLE F - using Klass.multiton_id
#
class TC_Multiton_F < Test::Unit::TestCase
class Klass
include Multiton
def initialize( important, not_important )
@important, @not_important = important, not_important
end
def Klass.multiton_id(*args, &block)
# we consider only the first arg
important, not_important = *args
important
end
end
def test_using_id
a = Klass.instance( :a, :b )
b = Klass.instance( :a, :c )
c = Klass.instance( :b, :b )
assert_equal( a, b )
assert_not_equal( a, c )
assert_not_equal( b, c )
end
end
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