44 lines
910 B
Ruby
44 lines
910 B
Ruby
# Singleton module that ensures only one object to be allocated.
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#
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# Usage:
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# class SomeSingletonClass
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# include Singleton
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# #....
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# end
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# a = SomeSingletonClass.instance
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# b = SomeSingletonClass.instance # a and b are same object
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# p [a,b]
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# a = SomeSingletonClass.new # error (`new' is private)
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module Singleton
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def Singleton.included(klass)
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klass.private_class_method(:new)
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klass.instance_eval %{
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@__instance__ = nil
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def instance
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unless @__instance__
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Thread.critical = true
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begin
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@__instance__ ||= new
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ensure
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Thread.critical = false
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end
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end
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return @__instance__
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end
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}
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end
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end
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if __FILE__ == $0
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class SomeSingletonClass
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include Singleton
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#....
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end
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a = SomeSingletonClass.instance
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b = SomeSingletonClass.instance # a and b are same object
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p [a,b]
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a = SomeSingletonClass.new # error (`new' is private)
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end
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