call_one

main.rb

def call_one &block
	result = nil
	proc { |*args| result ||= instance_exec(*args, &block) }
end

twice = call_one { |a| a + a }
p twice.call "homu"
p twice.call "mami"


class X
	define_method(:initialize, &call_one do
		p "init"
		@name = "mado"
	end)
end

p X.new.instance_eval { @name }
p X.new.instance_eval { @name }