Difference between `is_a?` and `instance_of?`

tc_is_a_vs_instance_of.rb

require 'test/unit'

class TestInstanceOf < Test::Unit::TestCase
  
  def test_string_is_a_string
    assert "string".is_a? String
  end
  
  def test_string_instance_of_string
    assert "string".instance_of? String
  end
  
  def test_string_is_a_object
    assert "string".is_a? Object
  end
  
  def test_string_not_instance_of_object
    # found this interesting. This could be useful where you want more strict check.
    assert_equal false, "string".instance_of? Object
  end

end

So use is_a? when any subclass will do. Use instance_of? when you want a specific type.