--- instance_variable_get(var)

    ruby 1.8 feature

    ֥ȤΥ󥹥ѿ var ֤ͤޤ
    󥹥ѿƤʤ nil ֤ޤ
    ѿ̾ var ʸ Symbol ǻꤷޤ

        class Foo
          def initialize
            @foo = 1
          end
        end

        obj = Foo.new
        p obj.instance_variable_get("@foo")     # => 1
        p obj.instance_variable_get(:@foo)      # => 1
        p obj.instance_variable_get(:@bar)      # => nil

