Procuration en C#
La Procuration est un patron de conception structurel qui fournit un objet qui agit comme un substitut pour un objet du service utilisé par un client. Une procuration reçoit les demandes d’un client, effectue des tâches (contrôle des accès, mise en cache, etc.) et passe ensuite la demande à un objet du service.
L’objet Procuration possède la même interface qu’un service, ce qui le rend interchangeable avec un vrai objet lorsqu’il est passé à un client.
Complexité :
Popularité :
Exemples d’utilisation : La procuration n’est pas souvent invitée en C#, mais elle se montre très pratique dans certains cas. Elle est incontournable lorsque vous voulez ajouter de nouveaux comportements à un objet d’une classe existante sans modifier le code client.
Identification : Les procurations délèguent tout le travail à un autre objet. Chaque méthode de la procuration devrait au final, faire référence à un objet du service, sauf si la procuration est une sous-classe d’un service.
Exemple conceptuel
Dans cet exemple, nous allons voir la structure de la Procuration. Nous allons répondre aux questions suivantes :
- Que contiennent les classes ?
- Quels rôles jouent-elles ?
- Comment les éléments du patron sont-ils reliés ?
Program.cs: Exemple conceptuel
using System;
namespace RefactoringGuru.DesignPatterns.Proxy.Conceptual
{
// The Subject interface declares common operations for both RealSubject and
// the Proxy. As long as the client works with RealSubject using this
// interface, you'll be able to pass it a proxy instead of a real subject.
public interface ISubject
{
void Request();
}
// The RealSubject contains some core business logic. Usually, RealSubjects
// are capable of doing some useful work which may also be very slow or
// sensitive - e.g. correcting input data. A Proxy can solve these issues
// without any changes to the RealSubject's code.
class RealSubject : ISubject
{
public void Request()
{
Console.WriteLine("RealSubject: Handling Request.");
}
}
// The Proxy has an interface identical to the RealSubject.
class Proxy : ISubject
{
private RealSubject _realSubject;
public Proxy(RealSubject realSubject)
{
this._realSubject = realSubject;
}
// The most common applications of the Proxy pattern are lazy loading,
// caching, controlling the access, logging, etc. A Proxy can perform
// one of these things and then, depending on the result, pass the
// execution to the same method in a linked RealSubject object.
public void Request()
{
if (this.CheckAccess())
{
this._realSubject.Request();
this.LogAccess();
}
}
public bool CheckAccess()
{
// Some real checks should go here.
Console.WriteLine("Proxy: Checking access prior to firing a real request.");
return true;
}
public void LogAccess()
{
Console.WriteLine("Proxy: Logging the time of request.");
}
}
public class Client
{
// The client code is supposed to work with all objects (both subjects
// and proxies) via the Subject interface in order to support both real
// subjects and proxies. In real life, however, clients mostly work with
// their real subjects directly. In this case, to implement the pattern
// more easily, you can extend your proxy from the real subject's class.
public void ClientCode(ISubject subject)
{
// ...
subject.Request();
// ...
}
}
class Program
{
static void Main(string[] args)
{
Client client = new Client();
Console.WriteLine("Client: Executing the client code with a real subject:");
RealSubject realSubject = new RealSubject();
client.ClientCode(realSubject);
Console.WriteLine();
Console.WriteLine("Client: Executing the same client code with a proxy:");
Proxy proxy = new Proxy(realSubject);
client.ClientCode(proxy);
}
}
}
Output.txt: Résultat de l’exécution
Client: Executing the client code with a real subject:
RealSubject: Handling Request.
Client: Executing the same client code with a proxy:
Proxy: Checking access prior to firing a real request.
RealSubject: Handling Request.
Proxy: Logging the time of request.
