blob: 8167a01aa8986982bcb6c8ae0457cef883e7f297 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
|
# Singleton module that ensures only one object to be allocated.
#
# Usage:
# class SomeSingletonClass
# include Singleton
# #....
# end
# a = SomeSingletonClass.instance
# b = SomeSingletonClass.instance # a and b are same object
# p [a,b]
# a = SomeSingletonClass.new # error (`new' is private)
module Singleton
def Singleton.append_features(klass)
klass.private_class_method(:new)
klass.instance_eval %{
def instance
unless @__instance__
@__instance__ = new
end
return @__instance__
end
}
end
end
if __FILE__ == $0
class SomeSingletonClass
include Singleton
#....
end
a = SomeSingletonClass.instance
b = SomeSingletonClass.instance # a and b are same object
p [a,b]
a = SomeSingletonClass.new # error (`new' is private)
end
|
