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Code Like a Ninja Session 7 - Creational Design Patterns

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Deon Meyer
Deon Meyer

This document discusses creational design patterns including factory method, abstract factory, and simple factory patterns. It provides definitions and examples of when each pattern should be used. The factory method pattern is used when classes delegate responsibility for object instantiation to subclasses, while abstract factory is used when families of related objects are designed to be used together and their instantiation must be consistent. Code examples are provided to illustrate simple factory, factory method, and abstract factory patterns. Session resources including presentation notes and code sources are also listed.

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CODE LIKE A NINJA CREATIONAL DESIGN PATTERNS
SESSION RESOURCES • Presentation session notes including link to this session, will be available on http://learningaboutfudge.blogspot.com • All the source for this session is publically available at: https://github.com/SheepWorx/Training • RSS Feed: http://learningaboutfudge.blogspot.com/feeds/posts/default?alt=rss • Local Network: dmeyer-msharetrainingCode Like a Ninja • Source was compiled using Visual Studio 2012 • http://www.gofpatterns.com/
Design Patterns Creational Design Patterns Structural Design Patterns Behavioral Design Patterns
CREATIONAL DESIGN PATTERNS Definition Creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation.
• Abstract Factory • Builder • Factory Method • Prototype • Singleton CREATIONAL DESIGN PATTERNS
FACTORY (ABSTRACT AND METHOD) • Lets a class defer instantiation into subclasses • Allows you to introduce new classes without modifying the code • Factory Method: when you need to delegate the creation of single objects • Abstract Factory: When you need to delegate the creation of families of related or dependant objects without specifying the concrete classes
SIMPLE FACTORY Client Factory Concrete Class 1 Concrete Class 2 Concrete Class 2 Base class/ interface
SIMPLE FACTORY • Classes that need to be instantiated need to inherit from a common class (abstract class or interface) • The factory will receive some form of identifier and create the correct concrete class • Will return it via its base class (abstract class or interface)
SIMPLE FACTORY See simple factory code example Question(s): What will happen when we need to add new types
FACTORY METHOD Client Concrete Factory 1 Concrete Factory 2 Base Factory Concrete Class 1 Concrete Class 2 Base class/ interface
FACTORY METHOD • Classes you want to create must inherit from a base object (abstract class or interface) • Each class will have its own factory • The factories themselves will inherit off a base factory (abstract class) • Base factory will control behaviour while individual factories will be responsible for returning concrete instances of the desired class • If unique logic exists for a particular class, I recommend it be encapsulated within its factory
FACTORY METHOD – WHEN TO USE IT It should be used when… • A class cannot anticipate the class of objects it must create • A class wants it subclasses to specify the objects it creates • Classes delegate responsibility to one of several helper classes and you want to localize the knowledge of which helper subclass is the delegate
FACTORY METHOD – BENEFITS • Eliminates the need to bind application classes to your code The code only deals with the interface • Enables subclasses to provide an extended version of an object because creating an object inside a class is more flexible than creating the object directly in the client
FACTORY METHOD See factory method code example
ABSTRACT FACTORY Client Abstract Factory Abstract Product A Abstract Product B Concrete Factory 1 Concrete Factory 2 Product A2 Product B2 Product B1 Product A1
ABSTRACT FACTORY • Provides an interface for creating families of related or dependant objects without specifying their concrete classes • The client interacts only with the product interfaces and the abstract factory class. It thus never knows about the concrete construction provided by this pattern • Abstract factory is similar to the factory method, except it creates families of related objects.
ABSTRACT FACTORY – WHEN TO USE IT It should be used when… • The system should be independent of how its products are created, composed and represented • The system should be configured with one of multiple families of products • The family of related product objects is designed to be used together and you must enforce this constraint.
ABSTRACT FACTORY– BENEFITS • Isolates concrete classes • Makes exchanging product families easy • Promotes consistency among products
ABSTRACT FACTORY See abstract factory code example
SESSION RESOURCES • Presentation session notes including link to this session, will be available on http://learningaboutfudge.blogspot.com • All the source for this session is publically available at: https://github.com/SheepWorx/Training • RSS Feed: http://learningaboutfudge.blogspot.com/feeds/posts/default?alt=rss • Local Network: dmeyer-msharetrainingCode Like a Ninja • Source was compiled using Visual Studio 2012 • http://www.gofpatterns.com/

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Code Like a Ninja Session 7 - Creational Design Patterns

  • 1. CODE LIKE A NINJA CREATIONAL DESIGN PATTERNS
  • 2. SESSION RESOURCES • Presentation session notes including link to this session, will be available on http://learningaboutfudge.blogspot.com • All the source for this session is publically available at: https://github.com/SheepWorx/Training • RSS Feed: http://learningaboutfudge.blogspot.com/feeds/posts/default?alt=rss • Local Network: dmeyer-msharetrainingCode Like a Ninja • Source was compiled using Visual Studio 2012 • http://www.gofpatterns.com/
  • 3. Design Patterns Creational Design Patterns Structural Design Patterns Behavioral Design Patterns
  • 4. CREATIONAL DESIGN PATTERNS Definition Creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation.
  • 5. • Abstract Factory • Builder • Factory Method • Prototype • Singleton CREATIONAL DESIGN PATTERNS
  • 6. FACTORY (ABSTRACT AND METHOD) • Lets a class defer instantiation into subclasses • Allows you to introduce new classes without modifying the code • Factory Method: when you need to delegate the creation of single objects • Abstract Factory: When you need to delegate the creation of families of related or dependant objects without specifying the concrete classes
  • 7. SIMPLE FACTORY Client Factory Concrete Class 1 Concrete Class 2 Concrete Class 2 Base class/ interface
  • 8. SIMPLE FACTORY • Classes that need to be instantiated need to inherit from a common class (abstract class or interface) • The factory will receive some form of identifier and create the correct concrete class • Will return it via its base class (abstract class or interface)
  • 9. SIMPLE FACTORY See simple factory code example Question(s): What will happen when we need to add new types
  • 10. FACTORY METHOD Client Concrete Factory 1 Concrete Factory 2 Base Factory Concrete Class 1 Concrete Class 2 Base class/ interface
  • 11. FACTORY METHOD • Classes you want to create must inherit from a base object (abstract class or interface) • Each class will have its own factory • The factories themselves will inherit off a base factory (abstract class) • Base factory will control behaviour while individual factories will be responsible for returning concrete instances of the desired class • If unique logic exists for a particular class, I recommend it be encapsulated within its factory
  • 12. FACTORY METHOD – WHEN TO USE IT It should be used when… • A class cannot anticipate the class of objects it must create • A class wants it subclasses to specify the objects it creates • Classes delegate responsibility to one of several helper classes and you want to localize the knowledge of which helper subclass is the delegate
  • 13. FACTORY METHOD – BENEFITS • Eliminates the need to bind application classes to your code The code only deals with the interface • Enables subclasses to provide an extended version of an object because creating an object inside a class is more flexible than creating the object directly in the client
  • 14. FACTORY METHOD See factory method code example
  • 15. ABSTRACT FACTORY Client Abstract Factory Abstract Product A Abstract Product B Concrete Factory 1 Concrete Factory 2 Product A2 Product B2 Product B1 Product A1
  • 16. ABSTRACT FACTORY • Provides an interface for creating families of related or dependant objects without specifying their concrete classes • The client interacts only with the product interfaces and the abstract factory class. It thus never knows about the concrete construction provided by this pattern • Abstract factory is similar to the factory method, except it creates families of related objects.
  • 17. ABSTRACT FACTORY – WHEN TO USE IT It should be used when… • The system should be independent of how its products are created, composed and represented • The system should be configured with one of multiple families of products • The family of related product objects is designed to be used together and you must enforce this constraint.
  • 18. ABSTRACT FACTORY– BENEFITS • Isolates concrete classes • Makes exchanging product families easy • Promotes consistency among products
  • 19. ABSTRACT FACTORY See abstract factory code example
  • 20. SESSION RESOURCES • Presentation session notes including link to this session, will be available on http://learningaboutfudge.blogspot.com • All the source for this session is publically available at: https://github.com/SheepWorx/Training • RSS Feed: http://learningaboutfudge.blogspot.com/feeds/posts/default?alt=rss • Local Network: dmeyer-msharetrainingCode Like a Ninja • Source was compiled using Visual Studio 2012 • http://www.gofpatterns.com/

Editor's Notes

  1. Basic srpExposeutils class antipatternExpose singleton as a bad pattern to use (use at own risk)