Factory and Abstract Factory

Design Patterns 05/28/10 Week 3: Factory Method and Abstract Factory Jonathan Simon [email_address]

Agenda ,[object Object],[object Object],[object Object],[object Object],05/28/10

Head First Webpage ,[object Object],[object Object],[object Object],[object Object],05/28/10

Tangent : Preventing Future Mistakes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Preventing Future Mistakes (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 The method DoSomething() is overwriting behavior in the superclass.

Preventing Future Mistakes (cont) ,[object Object],[object Object],[object Object],[object Object],05/28/10

Preventing Future Mistakes (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Technical Debt 05/28/10 Source: http://martinfowler.com/bliki/TechnicalDebtQuadrant.html

Review: What Pattern should we consider? ,[object Object],[object Object],[object Object],05/28/10

Today’s Class ,[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Pizza Store in Objectville ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

PizzaStore in Objectville ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

PizzaStore in Objectville (pg 112 top) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 This method is responsible for creating the pizza. It calls methods to prepare, bake, etc. Pizza is returned to caller.

PizzaStore in Objectville (pg 112 middle) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Code that varies A parameter indicating type Code that stays the same

PizzaStore in Objectville (cont) ,[object Object],[object Object],[object Object],05/28/10

Solution? (pg 115) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

SimplePizzaFactory ,[object Object],[object Object],05/28/10

Rework of PizzaStore (pg 116) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Store is composed of a factory. Creation of pizza is delegated to factory.

Simple Factory Defined (pg 117) ,[object Object],[object Object],[object Object],[object Object],05/28/10

Change Now Occurs… ,[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Example (pg 119) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

More change happens… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

More change happens… (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

What New York wants ,[object Object],[object Object],[object Object],05/28/10

A Framework for Pizza Store (pg 120) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 NOTE : We are using inheritance here to create the pizzas, not composition. Also, the constructor for PizzaStore has been removed.

NYPizzaStore (pg 123) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 The subclass is defining how the pizza is created….and it is also providing unique functionality that is applicable to New York.

Factory Method ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Factory Method simply sets up an interface for creating a Product (in this case, a type of Pizza). Subclasses decide which specific Product to create.

Test Drive (pg 127) ,[object Object],[object Object],[object Object],[object Object],05/28/10

Factory Method Defined ,[object Object],05/28/10

Definitions (pg 134) ,[object Object],[object Object],[object Object],[object Object],05/28/10

IMPORTANT ,[object Object],05/28/10

Lab ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 ,[object Object],[object Object],[object Object],[object Object]

Parameterized Factory Method ,[object Object],[object Object],[object Object],05/28/10

Simple Factory Method ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Simple Factory Method (with Default) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 In this example, there is default Product created (DefaultPizza).

Back to SimUDuck (pg 16) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Developer would have to know to do this. The design does not enforce it. MallardDuck is tied to two specific implementations.

Before ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

After ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Factory Methods

Now we create MallardDuck… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Developer is “forced” to specify implementations of Fly and Quack. Note that the constructor is empty.

Alternative Design: Default Behavior ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 MallardDuck does not have to implement these methods.

Factory Method and Template ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Example re-worked here

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Changes.. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Pizza ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Pizza becomes composed of different ingredients. Question: How do we get these ingredients associated with a Pizza??

One idea…Constructor w/many parameters ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Makes sense…whenever you create a pizza, you must specify these ingredients…

Rework NYPizzaStore ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 This will cause a lot of maintenance headaches!!! Imagine what happens when we create a new pizza! We know that we have a certain set of ingredients that are used for New York..yet we have to keep repeating that set with each constructor. Can we define this unique set just once??

PizzaIngredientFactory (pg 146) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Create an interface for creating the different ingredients of Pizza. Note that each ingredient of Pizza has a corresponding method defined in the interface.

NYPizzaIngredientFactory (pg 147) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Here we see the set of ingredients that are specific to the NY region. Note that each time a createXXX() method is called, a new instance is returned. This will be important later on.

CheesePizza (pg 150) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Instead of many ingredient parameters, we just pass one. Does this remind you of another pattern?? Creation delegated Note: Not all ingredients have to be used!

NYPizzaStore (pg 152) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 The specific ingredient factory is defined once for the NY region.

Abstract Factory Defined ,[object Object],05/28/10

Factory Method vs. Abstract Factory ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Database Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

DatabaseFactory ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10 Each database implementation (Oracle, SQL Server, etc) will need to create their own version of this DatabaseFactory. The specific DatabaseFactory must be sent to the constructor of the framework class DatabaseManager.

Abstract Factory and Singleton ,[object Object],[object Object],05/28/10

A more interesting case… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

What will happen?? ,[object Object],[object Object],05/28/10

Solution: Abstract Factory and Prototype ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Solution: Abstract Factory and Prototype ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Abstract Factory: Last Thoughts ,[object Object],[object Object],05/28/10

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],05/28/10

Factory and Abstract Factory

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Editor's Notes