Ancestor chaining in ruby

gistfile1.rb

module AAA
  def abc
    "abc in AAA"
  end

  def not_in_common
    "not_in_common in AAA"
  end

end

module BBB
  def abc
    "abc in BBB"
  end

end

class TestClass
  include AAA, BBB

end

class SeparateIncludes
  include AAA
  include BBB

end

t = TestClass.new
puts
puts "Ancestors of #{t.class} are #{t.class.ancestors}"
puts "TestClass#abc returns \"#{t.abc}\"" 
puts
puts "Includes on separate lines behave differently"
puts "SeparateIncludes ancestors: #{SeparateIncludes.ancestors}"
puts
puts "SeparateIncludes#abc returns \"#{SeparateIncludes.new.abc}\"" 

Output

Ancestors of TestClass are [TestClass, AAA, BBB, Object, Kernel, BasicObject]
TestClass#abc returns "abc in AAA"

Includes on separate lines behave differently
SeparateIncludes ancestors: [SeparateIncludes, BBB, AAA, Object, Kernel, BasicObject]

SeparateIncludes#abc returns "abc in BBB"

Method lookup proceeds up the ancestor chain.