class Suma
    private
        @poop = 5
    public
        def initialize(param=0)
            @valor = param
            @val = 10
        end
        def ver
            tmp
        end
    protected
        def tmp
            puts @valor + @val + @poop # error here
            # nil can't be coerced into Fixnum (TypeError)
        end
end

sum = Suma.new(20)
sum.ver