Il pattern
Abstract Factory fa parte dei cosiddetti
Creational patterns cioè di quel genere di pattern che si occupa di istanziare (creare) oggetti.
La sua peculiarità è quella di fornire una interfaccia per creare famiglie di oggetti connessi o dipendenti tra loro, in modo che non ci sia necessità da parte dei client di specificare i nomi delle classi concrete all'interno del proprio codice.
Vediamo il diagramma UML:
Di seguito riportiamo la sua realizzazione in C#
// Abstract Factory pattern -- Structural example
using System;
namespace DoFactory.GangOfFour.Abstract.Structural
{
/// <summary>
/// MainApp startup class for Structural
/// Abstract Factory Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
public static void Main()
{
// Abstract factory #1
AbstractFactory factory1 = new ConcreteFactory1();
Client client1 = new Client(factory1);
client1.Run();
// Abstract factory #2
AbstractFactory factory2 = new ConcreteFactory2();
Client client2 = new Client(factory2);
client2.Run();
// Wait for user input
Console.ReadKey();
}
}
/// <summary>
/// The 'AbstractFactory' abstract class
/// </summary>
abstract class AbstractFactory
{
public abstract AbstractProductA CreateProductA();
public abstract AbstractProductB CreateProductB();
}
/// <summary>
/// The 'ConcreteFactory1' class
/// </summary>
class ConcreteFactory1 : AbstractFactory
{
public override AbstractProductA CreateProductA()
{
return new ProductA1();
}
public override AbstractProductB CreateProductB()
{
return new ProductB1();
}
}
/// <summary>
/// The 'ConcreteFactory2' class
/// </summary>
class ConcreteFactory2 : AbstractFactory
{
public override AbstractProductA CreateProductA()
{
return new ProductA2();
}
public override AbstractProductB CreateProductB()
{
return new ProductB2();
}
}
/// <summary>
/// The 'AbstractProductA' abstract class
/// </summary>
abstract class AbstractProductA
{
}
/// <summary>
/// The 'AbstractProductB' abstract class
/// </summary>
abstract class AbstractProductB
{
public abstract void Interact(AbstractProductA a);
}
/// <summary>
/// The 'ProductA1' class
/// </summary>
class ProductA1 : AbstractProductA
{
}
/// <summary>
/// The 'ProductB1' class
/// </summary>
class ProductB1 : AbstractProductB
{
public override void Interact(AbstractProductA a)
{
Console.WriteLine(this.GetType().Name +
" interacts with " + a.GetType().Name);
}
}
/// <summary>
/// The 'ProductA2' class
/// </summary>
class ProductA2 : AbstractProductA
{
}
/// <summary>
/// The 'ProductB2' class
/// </summary>
class ProductB2 : AbstractProductB
{
public override void Interact(AbstractProductA a)
{
Console.WriteLine(this.GetType().Name +
" interacts with " + a.GetType().Name);
}
}
/// <summary>
/// The 'Client' class. Interaction environment for the products.
/// </summary>
class Client
{
private AbstractProductA _abstractProductA;
private AbstractProductB _abstractProductB;
// Constructor
public Client(AbstractFactory factory)
{
_abstractProductB = factory.CreateProductB();
_abstractProductA = factory.CreateProductA();
}
public void Run()
{
_abstractProductB.Interact(_abstractProductA);
}
}
}
L'Output prodotto da questo semplice programma sarà:
ProductB1 interacts with ProductA1
ProductB2 interacts with ProductA2
