summaryrefslogtreecommitdiff
path: root/lib/singleton.rb
diff options
context:
space:
mode:
authormatz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>1999-08-13 05:45:20 +0000
committermatz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>1999-08-13 05:45:20 +0000
commit65a5162550f58047974793cdc8067a970b2435c0 (patch)
tree082bb7d5568f3b2e36e3fe166e9f3039394fcf44 /lib/singleton.rb
parentfcd020c83028f5610d382e85a2df00223e12bd7e (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.rb37
1 files changed, 37 insertions, 0 deletions
diff --git a/lib/singleton.rb b/lib/singleton.rb
new file mode 100644
index 0000000..8167a01
--- /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