Poids mouche en Ruby

Le poids mouche est un patron de conception structurel qui permet à des programmes de limiter leur consommation de mémoire malgré un très grand nombre d’objets.

Ce patron est obtenu en partageant des parties de l’état d’un objet à plusieurs autres objets. En d’autres termes, le poids mouche économise de la RAM en mettant en cache les données identiques chez différents objets.

En savoir plus sur la patron Poids mouche

Complexité :

Popularité :

Exemples d’utilisation : Le poids mouche n’a qu’une seule utilité : minimiser l’utilisation de la mémoire. Si votre programme ne rencontre aucun problème de RAM, ignorez ce patron pour le moment.

Identification : Le poids mouche peut être reconnu par une méthode de création qui renvoie des objets du cache plutôt que d’en créer de nouveaux.

Exemple conceptuel

Dans cet exemple, nous allons voir la structure du Poids mouche. Nous allons répondre aux questions suivantes :

Que contiennent les classes ?
Quels rôles jouent-elles ?
Comment les éléments du patron sont-ils reliés ?

main.rb: Exemple conceptuel

require 'json'

# The Flyweight stores a common portion of the state (also called intrinsic
# state) that belongs to multiple real business entities. The Flyweight accepts
# the rest of the state (extrinsic state, unique for each entity) via its method
# parameters.
class Flyweight
  # @param [String] shared_state
  def initialize(shared_state)
    @shared_state = shared_state
  end

  # @param [String] unique_state
  def operation(unique_state)
    s = @shared_state.to_json
    u = unique_state.to_json
    print "Flyweight: Displaying shared (#{s}) and unique (#{u}) state."
  end
end

# The Flyweight Factory creates and manages the Flyweight objects. It ensures
# that flyweights are shared correctly. When the client requests a flyweight,
# the factory either returns an existing instance or creates a new one, if it
# doesn't exist yet.
class FlyweightFactory
  # @param [Hash] initial_flyweights
  def initialize(initial_flyweights)
    @flyweights = {}
    initial_flyweights.each do |state|
      @flyweights[get_key(state)] = Flyweight.new(state)
    end
  end

  # Returns a Flyweight's string hash for a given state.
  def get_key(state)
    state.sort.join('_')
  end

  # Returns an existing Flyweight with a given state or creates a new one.
  def get_flyweight(shared_state)
    key = get_key(shared_state)

    if !@flyweights.key?(key)
      puts "FlyweightFactory: Can't find a flyweight, creating new one."
      @flyweights[key] = Flyweight.new(shared_state)
    else
      puts 'FlyweightFactory: Reusing existing flyweight.'
    end

    @flyweights[key]
  end

  def list_flyweights
    puts "FlyweightFactory: I have #{@flyweights.size} flyweights:"
    print @flyweights.keys.join("\n")
  end
end

# @param [FlyweightFactory] factory
# @param [String] plates
# @param [String] owner
# @param [String] brand
# @param [String] model
# @param [String] color
def add_car_to_police_database(factory, plates, owner, brand, model, color)
  puts "\n\nClient: Adding a car to database."
  flyweight = factory.get_flyweight([brand, model, color])
  # The client code either stores or calculates extrinsic state and passes it to
  # the flyweight's methods.
  flyweight.operation([plates, owner])
end

# The client code usually creates a bunch of pre-populated flyweights in the
# initialization stage of the application.

factory = FlyweightFactory.new([
                                 %w[Chevrolet Camaro2018 pink],
                                 ['Mercedes Benz', 'C300', 'black'],
                                 ['Mercedes Benz', 'C500', 'red'],
                                 %w[BMW M5 red],
                                 %w[BMW X6 white]
                               ])

factory.list_flyweights

add_car_to_police_database(factory, 'CL234IR', 'James Doe', 'BMW', 'M5', 'red')

add_car_to_police_database(factory, 'CL234IR', 'James Doe', 'BMW', 'X1', 'red')

puts "\n\n"

factory.list_flyweights

output.txt: Résultat de l’exécution

FlyweightFactory: I have 5 flyweights:
Camaro2018_Chevrolet_pink
C300_Mercedes Benz_black
C500_Mercedes Benz_red
BMW_M5_red
BMW_X6_white

Client: Adding a car to database.
FlyweightFactory: Reusing existing flyweight.
Flyweight: Displaying shared (["BMW","M5","red"]) and unique (["CL234IR","James Doe"]) state.

Client: Adding a car to database.
FlyweightFactory: Can't find a flyweight, creating new one.
Flyweight: Displaying shared (["BMW","X1","red"]) and unique (["CL234IR","James Doe"]) state.

FlyweightFactory: I have 6 flyweights:
Camaro2018_Chevrolet_pink
C300_Mercedes Benz_black
C500_Mercedes Benz_red
BMW_M5_red
BMW_X6_white
BMW_X1_red

Poids mouche en Ruby

Exemple conceptuel

main.rb: Exemple conceptuel

output.txt: Résultat de l’exécution

Poids mouche dans les autres langues