Factory Pattern

Factory pattern is used to create objects. This pattern falls under creational patterns of GOF (Gang of Four) Patterns. In simple term factory used to create products and in software term factory used to create objects.

When to use –

When applications grow, we create more and more objects which increases complexity and becomes more difficult to maintain. To reduce complexity, we need to create objects in structured manner so that we can easily maintain them. Factory pattern provides easy way to create objects as per your need and also help you to write flexible and easy to maintain code.

Code –

public enum ResourceType

{

    DotNet,

    Java

}

public interface IResource

{

    string DoWork();

}

public class DotNet : IResource

{

    public string DoWork()

    {

        return "I'm writing Dotnet code.";

    }

}

public class Java : IResource

{

    public string DoWork()

    {

        return "I'm writing Java code.";

    }

}

public static class ResourceFactory

{

    public static IResource GetResource(ResourceType resourceType)

    {

        IResource resource;

        switch (resourceType)

        {

            case ResourceType.DotNet:

                resource = new DotNet();

                return resource;

            case ResourceType.Java:

                resource = new Java();

                return resource;

            default:

                resource = null;

                break;

        }

        return resource;

    }

}

class Program

{

    static void Main(string[] args)

    {

        IResource myResource = ResourceFactory.GetResource(ResourceType.DotNet);

        Console.WriteLine(myResource.DoWork());

        myResource = ResourceFactory.GetResource(ResourceType.Java);

        Console.WriteLine(myResource.DoWork());

        Console.ReadLine();

    }

}

Output –

Above example demonstrates how Factory Pattern used to get different types of resources as per customers need. This example can easily be extended by adding more resources.

Advantages –

• Factory patterns implementation provides loose coupling between application and factory products.
• Easy to extend and maintain products. (Open-Closed Principle)

Disadvantages –

• Sometimes it makes code more difficult to read.
• Increases complexity if incorrectly used.

Hope this post helps you to understand Factory Pattern. Please leave your feedback in comments below.

References –

MSDN

DoFactory

See Also –

Creational Patterns	Structural Patterns	Behavioral Patterns
Singleton Pattern	Adapter Pattern	Chain of Responsibility Pattern
Thread safe singleton pattern	Bridge Pattern	Command Pattern
Factory Pattern	Composite Pattern	Interpreter Pattern
Abstract Factory Pattern	Decorator Pattern	Iterator Pattern
Builder Pattern	Facade Pattern	Mediator Pattern
Prototype Pattern	Flyweight Pattern	Memento Pattern
	Proxy Pattern	Observer Pattern
		State Pattern
		Strategy Pattern
		Template Method Pattern
		Visitor Pattern