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author | matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 1999-08-13 05:45:20 +0000 |
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committer | matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 1999-08-13 05:45:20 +0000 |
commit | 65a5162550f58047974793cdc8067a970b2435c0 (patch) | |
tree | 082bb7d5568f3b2e36e3fe166e9f3039394fcf44 /lib/singleton.rb | |
parent | fcd020c83028f5610d382e85a2df00223e12bd7e (diff) |
1.4.0
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@520 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 |