localize_method.rb

#!ruby

class Foo
	def hello
		puts "Hello"
	end
end

def localize_method(klass, method, &block)
	unbound = klass.instance_method(method)
	klass.send(:define_method, method) do
		block.call(unbound.bind(self))
	end
	lambda {
		klass.send(:define_method, method, unbound)
	}
end

foo = Foo.new

foo.hello
#=> Hello

puts "===="

release = localize_method(Foo, :hello) do |orig|
	puts "before hello"
	orig.call
	puts "after hello"
end

foo.hello
#=> before hello
#   Hello
#   after hello

release.call

puts "===="

foo.hello
#=> Hello