Abstract Factory Design Pattern
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Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
Frequency of use:  high
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The classes and/or objects participating in this pattern are:
- AbstractFactory (ContinentFactory)
- declares an interface for operations that create abstract products
- ConcreteFactory (AfricaFactory, AmericaFactory)
- implements the operations to create concrete product objects
- AbstractProduct (Herbivore, Carnivore)
- declares an interface for a type of product object
- Product (Wildebeest, Lion, Bison, Wolf)
- defines a product object to be created by the corresponding concrete factory
- implements the AbstractProduct interface
- Client (AnimalWorld)
- uses interfaces declared by AbstractFactory and AbstractProduct classes
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.
Show code
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// Abstract Factory pattern -- Structural example
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using System;
namespace DoFactory.GangOfFour.Abstract.Structural
{
// MainApp test application
class MainApp
{
public static void Main()
{
// Abstract factory #1
AbstractFactory factory1 = new ConcreteFactory1();
Client c1 = new Client(factory1);
c1.Run();
// Abstract factory #2
AbstractFactory factory2 = new ConcreteFactory2();
Client c2 = new Client(factory2);
c2.Run();
// Wait for user input
Console.Read();
}
}
// "AbstractFactory"
abstract class AbstractFactory
{
public abstract AbstractProductA CreateProductA();
public abstract AbstractProductB CreateProductB();
}
// "ConcreteFactory1"
class ConcreteFactory1 : AbstractFactory
{
public override AbstractProductA CreateProductA()
{
return new ProductA1();
}
public override AbstractProductB CreateProductB()
{
return new ProductB1();
}
}
// "ConcreteFactory2"
class ConcreteFactory2 : AbstractFactory
{
public override AbstractProductA CreateProductA()
{
return new ProductA2();
}
public override AbstractProductB CreateProductB()
{
return new ProductB2();
}
}
// "AbstractProductA"
abstract class AbstractProductA
{
}
// "AbstractProductB"
abstract class AbstractProductB
{
public abstract void Interact(AbstractProductA a);
}
// "ProductA1"
class ProductA1 : AbstractProductA
{
}
// "ProductB1"
class ProductB1 : AbstractProductB
{
public override void Interact(AbstractProductA a)
{
Console.WriteLine(this.GetType().Name +
" interacts with " + a.GetType().Name);
}
}
// "ProductA2"
class ProductA2 : AbstractProductA
{
}
// "ProductB2"
class ProductB2 : AbstractProductB
{
public override void Interact(AbstractProductA a)
{
Console.WriteLine(this.GetType().Name +
" interacts with " + a.GetType().Name);
}
}
// "Client" - the interaction environment of the products
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);
}
}
}
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Output
ProductB1 interacts with ProductA1
ProductB2 interacts with ProductA2
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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.
Show code
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// Abstract Factory pattern -- Real World example
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using System;
namespace DoFactory.GangOfFour.Abstract.RealWorld
{
// MainApp test application
class MainApp
{
public static void Main()
{
// Create and run the Africa animal world
ContinentFactory africa = new AfricaFactory();
AnimalWorld world = new AnimalWorld(africa);
world.RunFoodChain();
// Create and run the America animal world
ContinentFactory america = new AmericaFactory();
world = new AnimalWorld(america);
world.RunFoodChain();
// Wait for user input
Console.Read();
}
}
// "AbstractFactory"
abstract class ContinentFactory
{
public abstract Herbivore CreateHerbivore();
public abstract Carnivore CreateCarnivore();
}
// "ConcreteFactory1"
class AfricaFactory : ContinentFactory
{
public override Herbivore CreateHerbivore()
{
return new Wildebeest();
}
public override Carnivore CreateCarnivore()
{
return new Lion();
}
}
// "ConcreteFactory2"
class AmericaFactory : ContinentFactory
{
public override Herbivore CreateHerbivore()
{
return new Bison();
}
public override Carnivore CreateCarnivore()
{
return new Wolf();
}
}
// "AbstractProductA"
abstract class Herbivore
{
}
// "AbstractProductB"
abstract class Carnivore
{
public abstract void Eat(Herbivore h);
}
// "ProductA1"
class Wildebeest : Herbivore
{
}
// "ProductB1"
class Lion : Carnivore
{
public override void Eat(Herbivore h)
{
// Eat Wildebeest
Console.WriteLine(this.GetType().Name +
" eats " + h.GetType().Name);
}
}
// "ProductA2"
class Bison : Herbivore
{
}
// "ProductB2"
class Wolf : Carnivore
{
public override void Eat(Herbivore h)
{
// Eat Bison
Console.WriteLine(this.GetType().Name +
" eats " + h.GetType().Name);
}
}
// "Client"
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);
}
}
}
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Output
Lion eats Wildebeest
Wolf eats Bison
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This .NET optimized code demonstrates the
same real-world situation as above but uses modern, built-in .NET features.
Show code
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// Abstract Factory pattern -- .NET optimized
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See our Singleton page for a .NET optimized code sample.
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