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Monteur

Monteur en C++

Le Monteur est un patron de conception de création qui permet de construire des objets complexes étape par étape.

Le monteur n’est pas comme les autres patrons de création : les produits n’ont pas besoin d’avoir une interface commune. Il est ainsi possible de créer différents produits en utilisant le même procédé de fabrication.

Utilisation du patron de conception en C++

Complexité :

Popularité :

Exemples d’utilisation : Le monteur est bien connu dans le monde du C++. Il se montre très utile lorsque vous devez créer un objet possédant de nombreuses configurations possibles.

Identification : Le monteur peut être identifié à l’intérieur d’une classe qui n’a qu’une seule méthode de création et plusieurs méthodes permettant de configurer l’objet en résultant. Les méthodes du monteur prennent souvent en charge le chaînage (par exemple, someBuilder->setValueA(1)->setValueB(2)->create()).

Exemple conceptuel

Dans cet exemple, nous allons voir la structure du patron de conception Monteur. Nous allons répondre aux questions suivantes :

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

main.cc: Exemple conceptuel

/**
 * It makes sense to use the Builder pattern only when your products are quite
 * complex and require extensive configuration.
 *
 * Unlike in other creational patterns, different concrete builders can produce
 * unrelated products. In other words, results of various builders may not
 * always follow the same interface.
 */

class Product1{
    public:
    std::vector<std::string> parts_;
    void ListParts()const{
        std::cout << "Product parts: ";
        for (size_t i=0;i<parts_.size();i++){
            if(parts_[i]== parts_.back()){
                std::cout << parts_[i];
            }else{
                std::cout << parts_[i] << ", ";
            }
        }
        std::cout << "\n\n"; 
    }
};


/**
 * The Builder interface specifies methods for creating the different parts of
 * the Product objects.
 */
class Builder{
    public:
    virtual ~Builder(){}
    virtual void ProducePartA() const =0;
    virtual void ProducePartB() const =0;
    virtual void ProducePartC() const =0;
};
/**
 * The Concrete Builder classes follow the Builder interface and provide
 * specific implementations of the building steps. Your program may have several
 * variations of Builders, implemented differently.
 */
class ConcreteBuilder1 : public Builder{
    private:

    Product1* product;

    /**
     * A fresh builder instance should contain a blank product object, which is
     * used in further assembly.
     */
    public:

    ConcreteBuilder1(){
        this->Reset();
    }

    ~ConcreteBuilder1(){
        delete product;
    }

    void Reset(){
        this->product= new Product1();
    }
    /**
     * All production steps work with the same product instance.
     */

    void ProducePartA()const override{
        this->product->parts_.push_back("PartA1");
    }

    void ProducePartB()const override{
        this->product->parts_.push_back("PartB1");
    }

    void ProducePartC()const override{
        this->product->parts_.push_back("PartC1");
    }

    /**
     * Concrete Builders are supposed to provide their own methods for
     * retrieving results. That's because various types of builders may create
     * entirely different products that don't follow the same interface.
     * Therefore, such methods cannot be declared in the base Builder interface
     * (at least in a statically typed programming language). Note that PHP is a
     * dynamically typed language and this method CAN be in the base interface.
     * However, we won't declare it there for the sake of clarity.
     *
     * Usually, after returning the end result to the client, a builder instance
     * is expected to be ready to start producing another product. That's why
     * it's a usual practice to call the reset method at the end of the
     * `getProduct` method body. However, this behavior is not mandatory, and
     * you can make your builders wait for an explicit reset call from the
     * client code before disposing of the previous result.
     */

    /**
     * Please be careful here with the memory ownership. Once you call
     * GetProduct the user of this function is responsable to release this
     * memory. Here could be a better option to use smart pointers to avoid
     * memory leaks
     */

    Product1* GetProduct() {
        Product1* result= this->product;
        this->Reset();
        return result;
    }
};

/**
 * The Director is only responsible for executing the building steps in a
 * particular sequence. It is helpful when producing products according to a
 * specific order or configuration. Strictly speaking, the Director class is
 * optional, since the client can control builders directly.
 */
class Director{
    /**
     * @var Builder
     */
    private:
    Builder* builder;
    /**
     * The Director works with any builder instance that the client code passes
     * to it. This way, the client code may alter the final type of the newly
     * assembled product.
     */

    public:

    void set_builder(Builder* builder){
        this->builder=builder;
    }

    /**
     * The Director can construct several product variations using the same
     * building steps.
     */

    void BuildMinimalViableProduct(){
        this->builder->ProducePartA();
    }
    
    void BuildFullFeaturedProduct(){
        this->builder->ProducePartA();
        this->builder->ProducePartB();
        this->builder->ProducePartC();
    }
};
/**
 * The client code creates a builder object, passes it to the director and then
 * initiates the construction process. The end result is retrieved from the
 * builder object.
 */
/**
 * I used raw pointers for simplicity however you may prefer to use smart
 * pointers here
 */
void ClientCode(Director& director)
{
    ConcreteBuilder1* builder = new ConcreteBuilder1();
    director.set_builder(builder);
    std::cout << "Standard basic product:\n"; 
    director.BuildMinimalViableProduct();
    
    Product1* p= builder->GetProduct();
    p->ListParts();
    delete p;

    std::cout << "Standard full featured product:\n"; 
    director.BuildFullFeaturedProduct();

    p= builder->GetProduct();
    p->ListParts();
    delete p;

    // Remember, the Builder pattern can be used without a Director class.
    std::cout << "Custom product:\n";
    builder->ProducePartA();
    builder->ProducePartC();
    p=builder->GetProduct();
    p->ListParts();
    delete p;

    delete builder;
}

int main(){
    Director* director= new Director();
    ClientCode(*director);
    delete director;
    return 0;    
}

Output.txt: Résultat de l’exécution

Standard basic product:
Product parts: PartA1

Standard full featured product:
Product parts: PartA1, PartB1, PartC1

Custom product:
Product parts: PartA1, PartC1

Monteur dans les autres langues

Patrons de conception : Monteur en Java Patrons de conception : Monteur en C# Patrons de conception : Monteur en PHP Patrons de conception : Monteur en Python Patrons de conception : Monteur en Ruby Patrons de conception : Monteur en Swift Patrons de conception : Monteur en TypeScript Patrons de conception : Monteur en Go