Fabrique en TypeScript
La Fabrique est un patron de conception de création qui permet de créer des produits sans avoir à préciser leurs classes concrètes.
La fabrique définit une méthode qui doit être utilisée pour créer des objets à la place de l’appel au constructeur (opérateur new). Les sous-classes peuvent redéfinir cette méthode pour modifier la classe des objets qui seront créés.
Lisez notre Comparaison des fabriques si vous avez du mal à saisir la différence entre les divers concepts et patrons.
Complexité :
Popularité :
Exemples d’utilisation : La fabrique est très largement utilisée en TypeScript. Elle est très utile lorsque vous avez besoin de flexibilité dans votre code.
Identification : La fabrique peut être reconnue grâce à ses méthodes de création qui produisent des objets depuis les classes concrètes, mais les retournent en tant qu’objets d’interface ou de type abstrait.
Exemple conceptuel
Dans cet exemple, nous allons voir la structure de la Fabrique et répondre aux questions suivantes :
- Que contiennent les classes ?
- Quels rôles jouent-elles ?
- Comment les éléments du patron sont-ils reliés ?
index.ts: Exemple conceptuel
/**
* The Creator class declares the factory method that is supposed to return an
* object of a Product class. The Creator's subclasses usually provide the
* implementation of this method.
*/
abstract class Creator {
/**
* Note that the Creator may also provide some default implementation of the
* factory method.
*/
public abstract factoryMethod(): Product;
/**
* Also note that, despite its name, the Creator's primary responsibility is
* not creating products. Usually, it contains some core business logic that
* relies on Product objects, returned by the factory method. Subclasses can
* indirectly change that business logic by overriding the factory method
* and returning a different type of product from it.
*/
public someOperation(): string {
// Call the factory method to create a Product object.
const product = this.factoryMethod();
// Now, use the product.
return `Creator: The same creator's code has just worked with ${product.operation()}`;
}
}
/**
* Concrete Creators override the factory method in order to change the
* resulting product's type.
*/
class ConcreteCreator1 extends Creator {
/**
* Note that the signature of the method still uses the abstract product
* type, even though the concrete product is actually returned from the
* method. This way the Creator can stay independent of concrete product
* classes.
*/
public factoryMethod(): Product {
return new ConcreteProduct1();
}
}
class ConcreteCreator2 extends Creator {
public factoryMethod(): Product {
return new ConcreteProduct2();
}
}
/**
* The Product interface declares the operations that all concrete products must
* implement.
*/
interface Product {
operation(): string;
}
/**
* Concrete Products provide various implementations of the Product interface.
*/
class ConcreteProduct1 implements Product {
public operation(): string {
return '{Result of the ConcreteProduct1}';
}
}
class ConcreteProduct2 implements Product {
public operation(): string {
return '{Result of the ConcreteProduct2}';
}
}
/**
* The client code works with an instance of a concrete creator, albeit through
* its base interface. As long as the client keeps working with the creator via
* the base interface, you can pass it any creator's subclass.
*/
function clientCode(creator: Creator) {
// ...
console.log('Client: I\'m not aware of the creator\'s class, but it still works.');
console.log(creator.someOperation());
// ...
}
/**
* The Application picks a creator's type depending on the configuration or
* environment.
*/
console.log('App: Launched with the ConcreteCreator1.');
clientCode(new ConcreteCreator1());
console.log('');
console.log('App: Launched with the ConcreteCreator2.');
clientCode(new ConcreteCreator2());
Output.txt: Résultat de l’exécution
App: Launched with the ConcreteCreator1.
Client: I'm not aware of the creator's class, but it still works.
Creator: The same creator's code has just worked with {Result of the ConcreteProduct1}
App: Launched with the ConcreteCreator2.
Client: I'm not aware of the creator's class, but it still works.
Creator: The same creator's code has just worked with {Result of the ConcreteProduct2}
