checking if a method is defined on the class

Question

How do I check if a method is defined on some class directly, not by inheritance or by inclusion/extension? I want something like \'foo?\' in the following:

clas         


        

Answer 1

Not exactly an answer to the question, but if you're reading this question, you might be interested in this, which uses .instance_methods(false)

class Object
  # This is more or less how Ruby does method lookup internally
  def who_responds_to?(method, klass_ancestors = nil)
    if klass_ancestors.nil?
      return who_responds_to?(method, self.class.ancestors)
    end

    if klass_ancestors.empty?
      return nil
    end

    if klass_ancestors[0].instance_methods(false).include?(method)
      return klass_ancestors[0]
    end

    klass_ancestors.shift

    who_responds_to?(method, klass_ancestors)
  end
end

For example

class Person
end

module Drummer
  def drum
  end
end

module Snowboarder
  def jump
  end
end

module Engineer
  def code
  end
end

class Bob < Person
  include Drummer
  include Snowboarder
  include Engineer

  def name
  end
end

puts "who responds to name"
puts bob.who_responds_to?(:name)
puts "\n"

puts "who responds to code"
puts bob.who_responds_to?(:code)
puts "\n"

puts "who responds to jump"
puts bob.who_responds_to?(:jump)
puts "\n"

puts "who responds to drum"
puts bob.who_responds_to?(:drum)
puts "\n"

puts "who responds to dance"
puts bob.who_responds_to?(:dance)

yields

who responds to name
Bob

who responds to code
Engineer

who responds to jump
Snowboarder

who responds to drum
Drummer

who responds to dance
[this line intentionally blank because return value is nil]