Dernière version du 7 juin 2020 à 15:28

Description

Provide a surrogate or placeholder for another object to control access to it.

Control access to an object
Proxy and subject objects share the same interface

Proxy vs decorator pattern

Decorator informs and empowers its client, it adds functionalities to an object.
The client knows those functionalities.
Proxy restricts and disempowers its client, it controls access to an object.
The client doesn't know those control access functionalities.

Exemple

public class User
{
    public string Name { get; set; }
}

IUserClient.cs

public interface IUserClient
{
    IReadOnlyList<User> GetUsers();
}

UserClient.cs

public class UserClient : IUserClient
{
    public IReadOnlyList<User> GetUsers()
    {
        return new[]
        {
            new User { Name = "Nicolas" },
            new User { Name = "Paul" }
        };
    }
}

ProxyUserClient

public class ProxyUserClient : IUserClient
{
    private UserClient userClient;

    public bool Authenticate(string userName, string password)
    {
        if (userName == "Nicolas" && password == "0000")
        {
            userClient = new UserClient();
            return true;
        }

        return false;
    }

    public IReadOnlyList<User> GetUsers() => userClient?.GetUsers();
}

IUserClient userClient = new UserClient();
// call GetUsers from UserClient: no restrictions
var users = userClient.GetUsers();
Console.WriteLine(string.Join('\n', users.Select(x => $"{x.Name}")));

userClient = new ProxyUserClient();

// authentication
((ProxyUserClient)userClient).Authenticate("Nicolas", "0000");

// call GetUsers from ProxyUserClient: authentication restriction
users = userClient.GetUsers();
if (users == null)
    Console.WriteLine("You need to authenticate first.");
else
    Console.WriteLine(string.Join('\n', users.Select(x => $"{x.Name}")));

@@ Ligne 2 : / Ligne 2 : @@
 [[Category:Design Patterns]]
 = Description =
-* proxy object controls the creation and access to the subject object
+Provide a surrogate or placeholder for another object to control access to it.
-* proxy and subject objects share the same interface
+* Control access to an object
+* Proxy and subject objects share the same interface
 == Proxy vs decorator pattern ==
-* Decorator informs and empowers its client, it adds functionalities to an object. The client knows those functionalities.
+* Decorator informs and empowers its client, it adds functionalities to an object.<br>The client knows those functionalities.
-* Proxy restricts and disempowers its client, it controls access to an object. The client doesn't know those control access functionalities.
+* Proxy restricts and disempowers its client, it controls access to an object.<br>The client doesn't know those control access functionalities.
 = Exemple =