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author | matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 1998-07-09 08:40:46 +0000 |
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committer | matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 1998-07-09 08:40:46 +0000 |
commit | 3c1d5b89c33546028fce534546b8e356369ee231 (patch) | |
tree | fb658b101bf9a045c488663f2cbc6b3a178bbd3e /lib/singleton.rb | |
parent | 528b1f5237bc4e031228a27c00cdd679319f2472 (diff) |
1.1b9_30
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/v1_1r@263 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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 |