• It provides a class that creates other objects that are related by a common interface.
  • This class creates families of related or dependent objects without specifying their concrete classes.
• Over time, its meaning has evolved relative to the original GoF definition.
  • Today, this pattern aims to create individual object instances.
• Constructors are limited in their control over the overall creation process.
  • They don’t communicate their intention very well because they must be named after their class.
  • Having numerous overloaded constructors may make it hard for the client developer to decide which constructor to use.
  • Replacing constructors with intention-revealing creation methods is frequently preferred.
  • If your application needs more control, consider using a Factory.
• Some possible scenarios where this may be the case are when the creation process involves object caching, sharing or re-using of objects, and maintaining object and type counts.
• There are times when the client does not know exactly what type to construct.
  • It is easier to code against a base type or an interface and then let a factory make this decision for the client.

Participants

• AbstractProduct (IVehicle)
  • Declares an interface for a type of Product object.
• Product (KiaPride, HyundaiAccent)
  • The implementation of the AbstractProduct interface.
• AbstractFactory (IVehicleFactory)
  • Declares an interface for operations that create AbstractProduct.
• ConcreteFactory (KiaFactory, HyundaiFactory)
  • Implements the operations to create concrete product objects.

var kiaFactory = new KiaFactory();
var kiaEconomy = kiaFactory.GetEconomyCar();
var kiaLuxury = kiaFactory.GetLuxuryCar();

var hyundaiFactory = new HyundaiFactory();
var hyundaiEconomy = hyundaiFactory.GetEconomyCar();
var hyundaiLuxury = hyundaiFactory.GetLuxuryCar();

public interface IVehicle
{
	string GetName();
}

public class KiaPride : IVehicle
{
	public string GetName() => "Kia - Pride";
}

public class KiaRegal : IVehicle
{
	public string GetName() => "Kia - Regal";
}

public class HyundaiAccent : IVehicle
{
	public string GetName() => "Hyundai - Accent";
}

public class HyundaiSantaFe : IVehicle
{
	public string GetName() => "Hyundai - SantaFe";
}

public interface IVehicleFactory
{
	IVehicle GetLuxuryCar();
	IVehicle GetEconomyCar();
}

public class KiaFactory : IVehicleFactory
{
	public IVehicle GetLuxuryCar() => new KiaPride();
	public IVehicle GetEconomyCar() => new KiaRegal();
}

public class HyundaiFactory : IVehicleFactory
{
	public IVehicle GetLuxuryCar() => new HyundaiAccent();
	public IVehicle GetEconomyCar() => new HyundaiSantaFe();
}

Rules of Thumb

• Abstract Factory, Builder, and Prototype define a factory object that's responsible for knowing and creating the class of product objects.
  • Abstract Factory has the factory object producing objects of several classes.
  • Builder has the factory object building a complex product incrementally using a correspondingly complex protocol.
  • Prototype has the factory object (aka prototype) building a product by copying a prototype object.
• Abstract Factory classes are often implemented with Factory Methods, but they can also be implemented using Prototype.
• Abstract Factory can be used as an alternative to Facade to hide platform-specific classes.
• Builder focuses on constructing a complex object step by step.
  • Abstract Factory emphasizes a family of product objects (either simple or complex).
  • Builder returns the product as a final step, but as far as the Abstract Factory is concerned, the product gets returned immediately.