memoized 9 examples

0_start.rb

#!/usr/bin/env ruby

class Routes
  def distance(*segments)
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


r = Routes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

1_in_method.rb

#!/usr/bin/env ruby

class Routes
  
  def initialize
    @distances = {}
  end
  
  def distance(*segments)
    # @distances[segments] ||= calculate_distance(*segments) # => only works if value != nil
    if @distances.has_key?(segments)
      @distances[segments]
    else
      @distances[segments] = calculate_distance(*segments)
    end
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


r = Routes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

2_sub_class.rb

#!/usr/bin/env ruby

class Routes
  def distance(*segments)
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


class MemoizedRoutes < Routes
  def initialize
    @distances = {}
  end
  
  def distance(*segments)
    if @distances.has_key?(segments)
      @distances[segments]
    else
      @distances[segments] = super
    end
  end
end

r = MemoizedRoutes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

3_subclass_generator.rb

#!/usr/bin/env ruby

class Routes
  def distance(*segments)
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  

def memoized(cls, method)
  Class.new(cls) do
    memory = {}

    define_method method do |*args|
      if memory.has_key?(args)
        memory[args]
      else
        memory[args] = super
      end
    end
  end
end


r = memoized(Routes, :distance).new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

4_eigen_class.rb

#!/usr/bin/env ruby

class Routes
  def distance(*segments)
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


r = Routes.new

def r.distance(*segments)
  @memory ||= {}
  if @memory.has_key?(segments)
    @memory[segments]
  else
    @memory[segments] = super
  end
end

puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

5_eigen_generator.rb

#!/usr/bin/env ruby

class Routes
  def distance(*segments)
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  

def memoize(obj, method)
  eigen = class << obj; self; end  # => here and the next line
  eigen.class_eval do
    memory ||= {}
    define_method method do |*args|
      if memory.has_key?(args)
        memory[args]
      else
        memory[args] = super
      end
    end
  end
end

r = Routes.new
memoize(r, :distance)

puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

6_alias_method.rb

#!/usr/bin/env ruby

class Routes
  def distance(*segments)
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  

class Routes
  alias_method :_original_distance_, :distance
  
  def distance(*segments)
    @memory ||= {}
    if @memory.has_key?(segments)
      @memory[segments]
    else
      @memory[segments] = _original_distance_(*segments)
    end
  end
end

r = Routes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

7_alias_method_module.rb

#!/usr/bin/env ruby
module Memoize
  def remember(name)
    original = "original #{name}"
    alias_method original, name
    
    memory ||= {}
    
    define_method name do |*args|
      if memory.has_key?(args)
        memory[args]
      else
        memory[args] = send original, *args
      end
    end
  end
end

class Routes
  extend Memoize
  
  def distance(*segments)
    calculate_distance(*segments)
  end
  
  remember :distance
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


r = Routes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

8_bind_rewrite.rb

#!/usr/bin/env ruby
module Memoize
  def remember(name)
    
    original_method = instance_method(name)
    
    memory ||= {}
    
    define_method name do |*args|
      if memory.has_key?(args)
        memory[args]
      else
        bound_method = original_method.bind(self)
        memory[args] = bound_method.call(*args)
      end
    end
  end
end

class Routes
  extend Memoize
  
  def distance(*segments)
    calculate_distance(*segments)
  end
  
  remember :distance
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


r = Routes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

9_bind_dsl.rb

#!/usr/bin/env ruby
module Memoize
  def remember(name, &block)
    
    define_method(name, &block)
    original_method = instance_method(name)
    
    memory ||= {}
    
    define_method name do |*args|
      if memory.has_key?(args)
        memory[args]
      else
        bound_method = original_method.bind(self)
        memory[args] = bound_method.call(*args)
      end
    end
  end
end

class Routes
  extend Memoize
    
  remember :distance do |*segments|
    calculate_distance(*segments)
  end
  
private  
  def calculate_distance(*segments)
    puts "Expensive Task"
    segments.inject { |sum, val| sum + val }
  end
end  


r = Routes.new
puts r.distance 1,2,3,4
puts r.distance 1,2,3,4
puts r.distance 9,8,7,6
puts r.distance 9,8,7,6

sample.rb

#!/usr/bin/env ruby