gistfile1.rb

class Example
  attr_accessor :var_1, :var_2

  def with_self(var)
    self.var_1 = var
  end

  def without_self(var)
    var_2 = var
  end
end

e = Example.new
e.with_self(:hello)
e.without_self(:world)

# Will be :hello
e.var_1

# Will be nil
e.var_2