Ruby load ruins whatever clever thing you were doing with alias_method

gistfile1.rb

# base.rb

class Base
  def foo
    puts "BASE"
  end
end

# derived.rb

require "./base"

class Derived < Base
  alias_method :foo_aliased, :foo  

  def foo
    puts "DERIVED!"
  end
end

# From the REPL:

load './derived.rb'
# => true
Derived.new.foo
# DERIVED!
# => nil
Derived.new.foo_aliased
# BASE
# => nil
load './derived.rb'
# => true
Derived.new.foo
# DERIVED!
# => nil
Derived.new.foo_aliased
# DERIVED!
# => nil