respond_to_missing? and BasicObject

gistfile1.rb

class A
  def initialize(obj)
    @obj = obj
  end
 
  def method_missing(message, *args, &block)
    @obj.send(message, *args, &block)
  end
end
 
class B < BasicObject
  def initialize(obj)
    @obj = obj
  end
 
  def method_missing(message, *args, &block)
    @obj.send(message, *args, &block)
  end
end
 
a = A.new("string")
a.upcase               #=> "STRING"
a.respond_to?(:upcase) #=> false
# a.method(:upcase)    # Raises NameError if we don't define respond_to_missing?
 
b = B.new("string")
b.upcase               #=> "STRING"
b.respond_to?(:upcase) #=> true
b.method(:upcase)      #=> #<Method: String#upcase>