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Prototype

Prototype en C++

Prototype es un patrón de diseño creacional que permite la clonación de objetos, incluso los complejos, sin acoplarse a sus clases específicas.

Todas las clases prototipo deben tener una interfaz común que haga posible copiar objetos incluso si sus clases concretas son desconocidas. Los objetos prototipo pueden producir copias completas, ya que los objetos de la misma clase pueden acceder a los campos privados de los demás.

Uso del patrón en C++

Complejidad:

Popularidad:

Ejemplos de uso: El patrón Prototype está disponible en C++ listo para usarse con una interfaz Cloneable.

Identificación: El prototipo puede reconocerse fácilmente por un método clone o copy, etc.

Ejemplo conceptual

Este ejemplo ilustra la estructura del patrón de diseño Prototype. Se centra en responder las siguientes preguntas:

  • ¿De qué clases se compone?
  • ¿Qué papeles juegan esas clases?
  • ¿De qué forma se relacionan los elementos del patrón?

main.cc: Ejemplo conceptual

using std::string;

// Prototype Design Pattern
//
// Intent: Lets you copy existing objects without making your code dependent on
// their classes.

enum Type {
  PROTOTYPE_1 = 0,
  PROTOTYPE_2
};

/**
 * The example class that has cloning ability. We'll see how the values of field
 * with different types will be cloned.
 */

class Prototype {
 protected:
  string prototype_name_;
  float prototype_field_;

 public:
  Prototype() {}
  Prototype(string prototype_name)
      : prototype_name_(prototype_name) {
  }
  virtual ~Prototype() {}
  virtual Prototype *Clone() const = 0;
  virtual void Method(float prototype_field) {
    this->prototype_field_ = prototype_field;
    std::cout << "Call Method from " << prototype_name_ << " with field : " << prototype_field << std::endl;
  }
};

/**
 * ConcretePrototype1 is a Sub-Class of Prototype and implement the Clone Method
 * In this example all data members of Prototype Class are in the Stack. If you
 * have pointers in your properties for ex: String* name_ ,you will need to
 * implement the Copy-Constructor to make sure you have a deep copy from the
 * clone method
 */

class ConcretePrototype1 : public Prototype {
 private:
  float concrete_prototype_field1_;

 public:
  ConcretePrototype1(string prototype_name, float concrete_prototype_field)
      : Prototype(prototype_name), concrete_prototype_field1_(concrete_prototype_field) {
  }

  /**
   * Notice that Clone method return a Pointer to a new ConcretePrototype1
   * replica. so, the client (who call the clone method) has the responsability
   * to free that memory. I you have smart pointer knowledge you may prefer to
   * use unique_pointer here.
   */
  Prototype *Clone() const override {
    return new ConcretePrototype1(*this);
  }
};

class ConcretePrototype2 : public Prototype {
 private:
  float concrete_prototype_field2_;

 public:
  ConcretePrototype2(string prototype_name, float concrete_prototype_field)
      : Prototype(prototype_name), concrete_prototype_field2_(concrete_prototype_field) {
  }
  Prototype *Clone() const override {
    return new ConcretePrototype2(*this);
  }
};

/**
 * In PrototypeFactory you have two concrete prototypes, one for each concrete
 * prototype class, so each time you want to create a bullet , you can use the
 * existing ones and clone those.
 */

class PrototypeFactory {
 private:
  std::unordered_map<Type, Prototype *, std::hash<int>> prototypes_;

 public:
  PrototypeFactory() {
    prototypes_[Type::PROTOTYPE_1] = new ConcretePrototype1("PROTOTYPE_1 ", 50.f);
    prototypes_[Type::PROTOTYPE_2] = new ConcretePrototype2("PROTOTYPE_2 ", 60.f);
  }

  /**
   * Be carefull of free all memory allocated. Again, if you have smart pointers
   * knowelege will be better to use it here.
   */

  ~PrototypeFactory() {
    delete prototypes_[Type::PROTOTYPE_1];
    delete prototypes_[Type::PROTOTYPE_2];
  }

  /**
   * Notice here that you just need to specify the type of the prototype you
   * want and the method will create from the object with this type.
   */
  Prototype *CreatePrototype(Type type) {
    return prototypes_[type]->Clone();
  }
};

void Client(PrototypeFactory &prototype_factory) {
  std::cout << "Let's create a Prototype 1\n";

  Prototype *prototype = prototype_factory.CreatePrototype(Type::PROTOTYPE_1);
  prototype->Method(90);
  delete prototype;

  std::cout << "\n";

  std::cout << "Let's create a Prototype 2 \n";

  prototype = prototype_factory.CreatePrototype(Type::PROTOTYPE_2);
  prototype->Method(10);

  delete prototype;
}

int main() {
  PrototypeFactory *prototype_factory = new PrototypeFactory();
  Client(*prototype_factory);
  delete prototype_factory;

  return 0;
}

Output.txt: Resultado de la ejecución

Let's create a Prototype 1
Call Method from PROTOTYPE_1  with field : 90

Let's create a Prototype 2 
Call Method from PROTOTYPE_2  with field : 10

Prototype en otros lenguajes

Patrones de diseño: Prototype en Java Patrones de diseño: Prototype en C# Patrones de diseño: Prototype en PHP Patrones de diseño: Prototype en Python Patrones de diseño: Prototype en Ruby Patrones de diseño: Prototype en Swift Patrones de diseño: Prototype en TypeScript Patrones de diseño: Prototype en Go