gistfile1.rb

class Example
  def make_method(&block)
    @block = block
  end
  
  def dynamic_method(n)
    @block.call(n) if @block
  end
end

example = Example.new

example.make_method do |n|
  n + 1
end

if example.dynamic_method(1) == 2
   puts "OK"
else
   puts "FAIL"
   puts "Expected 2, got #{example.dynamic_method(1).inspect}"
end