Factory Pattern
Content:
- Simple Factory
- Factory Method
- Abstract Factory
Create an instance of class
Yes.U can user new.And it’s so easy that mom need not to worry about i don’t know how to do it.But why Factory pattern?
Let’s say you have a pizza shop, and as a cutting-edge pizza store owner in Objectville you might end up writing some code like this:
public Pizza orderPizza(String type){
pizza = new Pizza();
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
return pizza;
}
But you need more than one type of pizza
public Pizza orderPizza(String type){
if (type.equals("cheese")) {
pizza = new CheesePizza();
} else if (type.equals("pepperoni")) {
pizza = new PepperoniPizza();
}
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
return pizza;
}
But the pressure is on to add more pizza types…
public class SimplePizzaFactory {
public Pizza createPizza(String type) {
Pizza pizza = null;
if (type.equals("cheese")) {
pizza = new CheesePizza();
} else if (type.equals("pepperoni")) {
pizza = new PepperoniPizza();
} else if (type.equals("clam")) {
pizza = new ClamPizza();
} else if (type.equals("veggie")) {
pizza = new VeggiePizza();
}
return pizza;
}
}
public class PizzaStore {
SimplePizzaFactory factory;
public PizzaStore(SimplePizzaFactory factory) {
this.factory = factory;
}
public Pizza orderPizza(String type) {
Pizza pizza;
pizza = factory.createPizza(type);
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
return pizza;
}
}
Franchising the pizza store with regional differences
public class NYPizzaStore extends PizzaStore {
Pizza createPizza(String item) {
if (item.equals("cheese")) {
return new NYStyleCheesePizza();
} else if (item.equals("veggie")) {
return new NYStyleVeggiePizza();
} else if (item.equals("clam")) {
return new NYStyleClamPizza();
} else if (item.equals("pepperoni")) {
return new NYStylePepperoniPizza();
} else return null;
}
}
public abstract class PizzaStore {
abstract Pizza createPizza(String item);
public Pizza orderPizza(String type) {
Pizza pizza = createPizza(type);
pizza.prepare();
. . .
return pizza;
}
}
Factory Method Pattern Definition
The Factory Method Pattern defines an interface for creating an object, but lets subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.
Abstract Factory
Provides an interface for creating families of related or dependent objects without specifying their concrete classes.