Design Patterns
By Faisal Jawaid

Builder Pattern

Builder Pattern is quite confusing. There is a very subtle difference between Builder Pattern and Factory Pattern. I am not discussing Factory Pattern in this article but will soon write about Factory Pattern as well.

In Builder Pattern the user is given the choice to create the type of object he wants but the construction process is the same.

We consider an example suppose you went to buy a car. First you will choose the model of the car and then it's color and you consider it's price that whether it's feasible for you or not and if you want some extra luxuries in the car you will note them down as well and in the end you will place the order. Now you are isolated with the manufacturing process. You are not bothered by the manufacturing process it's the duty of the company because they have the assembly plant, which is programmed to manufacture cars of the model you choose and the manufacturing process is same for a specified model of car.

In Builder the client instructs the builder class on how to create the object and then asks it for the result. How the class is put together is up to the Builder class

Class Diagram Showing Builder Pattern

Practical Implementation of Builder Pattern

Screen Shots

The Object Constructed according to user Selection

C# Implementation

IBuilder Interface

using System;
using System.Windows.Forms;  
namespace BuilderPattern
{
	/// 

	/// Summary description for IBuilder.
	/// 
	public interface IBuilder
	{		
		void MnaufactureCar();
	}
}

Classes that extends from IBuilder interface

1)	SuzukiMehran Class

       using System;
   using System.Windows.Forms;  

namespace BuilderPattern
{
	/// 

	/// Summary description for SuzukiMehran.
	/// 
	public class SuzukiMehran:IBuilder
	{
		public void MnaufactureCar()
		{
           MessageBox.Show("Suzuki Mehran Model 2002 "
			                +"Color Balck "
			                + "Air Conditioned " ); 
		}
	}
}


2)  SuzukiKhyber Class


          using System;
     using System.Windows.Forms;  

     namespace BuilderPattern
     {
	  /// 

	  /// Summary description for SuzukiKhyber.
	  /// 
	  public class SuzukiKhyber:IBuilder
	  {
		public SuzukiKhyber()
		{
			
		}

		public void MnaufactureCar()
		{
			MessageBox.Show("Suzuki Khyber Model 2002 Standard "
				+"Color Red "
				+"Air Conditioned "
				+"Alloy Rim "); 
		}
	   }
       }

Director class


  using System;

namespace BuilderPattern
{
	/// 

	/// Summary description for Director.
	/// 
	public class Director
	{
		public void ConstructCar(IBuilder build)
		{
			build.MnaufactureCar(); 
		}
	}
}


Client Class


private void button1_Click(object sender, System.EventArgs e)
		{
			if(cmbChooseCar.Text=="Suzuki Mehran")
  			 {
                Director car=new Director();
                IBuilder build=new SuzukiMehran();
                car.ConstructCar(build);  
			 }

			if(cmbChooseCar.Text=="Suzuki Khyber")
			 {
				Director car=new Director();
				IBuilder build=new SuzukiKhyber(); 
				car.ConstructCar(build);  
			 }
		}