Builder Pattern

The Builder Pattern is a software design pattern. The intention is to separate the construction of a complex object from its representation so that the same construction process can create different representations.

For better understanding please see below an example in C# language to make use of Builder Pattern.

//Implementation in C#.
class Pizza
{
string dough;
string sauce;
string topping;
public Pizza() {}
public void SetDough( string d){ dough = d;}
public void SetSauce( string s){ sauce = s;}
public void SetTopping( string t){ topping = t;}
}

//Abstract Builder
abstract class PizzaBuilder
{
protected Pizza pizza;
public PizzaBuilder(){}
public Pizza GetPizza(){ return pizza; }
public void CreateNewPizza() { pizza = new Pizza(); }

public abstract void BuildDough();
public abstract void BuildSauce();
public abstract void BuildTopping();
}

//Concrete Builder
class HawaiianPizzaBuilder : PizzaBuilder
{
public override void BuildDough() { pizza.SetDough("cross"); }
public override void BuildSauce() { pizza.SetSauce("mild"); }
public override void BuildTopping() { pizza.SetTopping("ham+pineapple"); }
}

//Concrete Builder
class SpicyPizzaBuilder : PizzaBuilder
{
public override void BuildDough() { pizza.SetDough("pan baked"); }
public override void BuildSauce() { pizza.SetSauce("hot"); }
public override void BuildTopping() { pizza.SetTopping("pepparoni+salami"); }
}

/** "Director" */
class Waiter {
private PizzaBuilder pizzaBuilder;

public void SetPizzaBuilder (PizzaBuilder pb) { pizzaBuilder = pb; }
public Pizza GetPizza() { return pizzaBuilder.GetPizza(); }

public void ConstructPizza() {
pizzaBuilder.CreateNewPizza();
pizzaBuilder.BuildDough();
pizzaBuilder.BuildSauce();
pizzaBuilder.BuildTopping();
}
}

/** A customer ordering a pizza. */
class BuilderExample
{
public static void Main(String[] args) {
Waiter waiter = new Waiter();
PizzaBuilder hawaiianPizzaBuilder = new HawaiianPizzaBuilder();
PizzaBuilder spicyPizzaBuilder = new SpicyPizzaBuilder();

waiter.SetPizzaBuilder ( hawaiianPizzaBuilder );
waiter.ConstructPizza();

Pizza pizza = waiter.GetPizza();
}
}