class Eren
include Comparable
attr_accessor :age
def initialize _age
@age = _age
end
def <=> other
self.age <=> other.age
end
end
e1 = Eren.new(10)
e2 = Eren.new(11)
e3 = Eren.new(2)
d = [e1,e2,e3].sort!
d.each do |x|
puts x.age
end