README.md

This demonstrates the difference in behaviour when using the public|protected|private_methods methods to check for the presence of a module method defined on Kernel or Object versus those defined in another Module.

module-method-existence.rb

class Object
  def method_in_object
    'method-in-object'
  end
end

module ModuleWithMethod
  def method_in_module
    'method-in-module'
  end
end

module Mod
  extend ModuleWithMethod
end

puts '# Calling module methods'
puts "Mod.method_in_object = #{Mod.method_in_object.inspect}"
puts "Mod.method_in_module = #{Mod.method_in_module.inspect}"
puts

puts '# Checking existence of Mod.method_in_object'
puts "Mod.public_methods(false) = #{Mod.public_methods(false).include?(:method_in_object)}"
puts "Mod.protected_methods(false) = #{Mod.protected_methods(false).include?(:method_in_object)}"
puts "Mod.private_methods(false) = #{Mod.private_methods(false).include?(:method_in_object)}"
puts "Mod.public_methods(true) = #{Mod.public_methods(true).include?(:method_in_object)}"
puts "Mod.protected_methods(true) = #{Mod.protected_methods(true).include?(:method_in_object)}"
puts "Mod.private_methods(true) = #{Mod.private_methods(true).include?(:method_in_object)}"
puts

puts '# Checking existence of Mod.method_in_module'
puts "Mod.public_methods(false) = #{Mod.public_methods(false).include?(:method_in_module)}"
puts "Mod.protected_methods(false) = #{Mod.protected_methods(false).include?(:method_in_module)}"
puts "Mod.private_methods(false) = #{Mod.private_methods(false).include?(:method_in_module)}"
puts "Mod.public_methods(true) = #{Mod.public_methods(true).include?(:method_in_module)}"
puts "Mod.protected_methods(true) = #{Mod.protected_methods(true).include?(:method_in_module)}"
puts "Mod.private_methods(true) = #{Mod.private_methods(true).include?(:method_in_module)}"

output.txt

# Calling module methods
Mod.method_in_object = "method-in-object"
Mod.method_in_module = "method-in-module"

# Checking existence of Mod.method_in_object
Mod.public_methods(false) = false
Mod.protected_methods(false) = false
Mod.private_methods(false) = false
Mod.public_methods(true) = true
Mod.protected_methods(true) = false
Mod.private_methods(true) = false

# Checking existence of Mod.method_in_module
Mod.public_methods(false) = true
Mod.protected_methods(false) = false
Mod.private_methods(false) = false
Mod.public_methods(true) = true
Mod.protected_methods(true) = false
Mod.private_methods(true) = false