The Abstract Factory design pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes.
A visualization of the classes and objects participating in this pattern.
The classes and objects participating in this pattern include:
ContinentFactory)
AfricaFactory, AmericaFactory)
Herbivore, Carnivore)
Wildebeest, Lion, Bison, Wolf)
AnimalWorld)
This structural code demonstrates the Abstract Factory pattern creating parallel hierarchies of objects. Object creation has been abstracted and there is no need for hard-coded class names in the client code.
copyusing 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);
}
}
}
This real-world code demonstrates the creation of different animal worlds for a computer game using different factories. Although the animals created by the Continent factories are different, the interactions among the animals remain the same.
using System;
namespace DoFactory.GangOfFour.Abstract.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Abstract Factory Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
public static void Main()
{
// Create and run the African animal world
ContinentFactory africa = new AfricaFactory();
AnimalWorld world = new AnimalWorld(africa);
world.RunFoodChain();
// Create and run the American animal world
ContinentFactory america = new AmericaFactory();
world = new AnimalWorld(america);
world.RunFoodChain();
// Wait for user input
Console.ReadKey();
}
}
/// <summary>
/// The 'AbstractFactory' abstract class
/// </summary>
abstract class ContinentFactory
{
public abstract Herbivore CreateHerbivore();
public abstract Carnivore CreateCarnivore();
}
/// <summary>
/// The 'ConcreteFactory1' class
/// </summary>
class AfricaFactory : ContinentFactory
{
public override Herbivore CreateHerbivore()
{
return new Wildebeest();
}
public override Carnivore CreateCarnivore()
{
return new Lion();
}
}
/// <summary>
/// The 'ConcreteFactory2' class
/// </summary>
class AmericaFactory : ContinentFactory
{
public override Herbivore CreateHerbivore()
{
return new Bison();
}
public override Carnivore CreateCarnivore()
{
return new Wolf();
}
}
/// <summary>
/// The 'AbstractProductA' abstract class
/// </summary>
abstract class Herbivore
{
}
/// <summary>
/// The 'AbstractProductB' abstract class
/// </summary>
abstract class Carnivore
{
public abstract void Eat(Herbivore h);
}
/// <summary>
/// The 'ProductA1' class
/// </summary>
class Wildebeest : Herbivore
{
}
/// <summary>
/// The 'ProductB1' class
/// </summary>
class Lion : Carnivore
{
public override void Eat(Herbivore h)
{
// Eat Wildebeest
Console.WriteLine(this.GetType().Name +
" eats " + h.GetType().Name);
}
}
/// <summary>
/// The 'ProductA2' class
/// </summary>
class Bison : Herbivore
{
}
/// <summary>
/// The 'ProductB2' class
/// </summary>
class Wolf : Carnivore
{
public override void Eat(Herbivore h)
{
// Eat Bison
Console.WriteLine(this.GetType().Name +
" eats " + h.GetType().Name);
}
}
/// <summary>
/// The 'Client' class
/// </summary>
class AnimalWorld
{
private Herbivore _herbivore;
private Carnivore _carnivore;
// Constructor
public AnimalWorld(ContinentFactory factory)
{
_carnivore = factory.CreateCarnivore();
_herbivore = factory.CreateHerbivore();
}
public void RunFoodChain()
{
_carnivore.Eat(_herbivore);
}
}
}
The .NET optimized code demonstrates the
same real-world situation as above but uses modern, built-in .NET features,
such as, generics, reflection, LINQ, lambda functions, etc.
You can find an example on our Singleton pattern page.
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