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Diffstat (limited to 'lib/singleton.rb')
| -rw-r--r-- | lib/singleton.rb | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/lib/singleton.rb b/lib/singleton.rb new file mode 100644 index 0000000000..8167a01aa8 --- /dev/null +++ b/lib/singleton.rb @@ -0,0 +1,37 @@ +# 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 |