topical media & game development

[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

pattern(s) / matrix / model(s) / resource(s)

design patterns

creational

factory
singleton
structural
adaptor
bridge
behavioral
strategy
observer

pattern(s) / matrix / model(s) / resource(s)

creational patterns

factory

provide interface for creating family of related or dependent objects without specifying their concrete classes

Example

also known as kit

participants

AbstractFactory, Concrete Factory, Abstract Product, Concrete Product

consequences

isolate concrete classes
makes exchanging product families easy
promotes consistency among products
supporting new kinds of products is difficult

implementation

See GOF

factory method

define interface for creating an object, but let subclass decide which class to instantiate

also know as

virtual constructor

motivation

encapsulates knowledge of which subclass to instantiate

applicability

when a class can not anticpate the class of the objects it creates
to delegate responsibility of object creation

structure

participants

Product, ConcreteProduct, Creator, ConcreteCreator

consequences

provide hooks for subclasses
connects parallel class hierarchies

Factory, Prototype

singleton

ensure a class has only one instance and provide a global point of access

applicability

only one instance of a class
instance must be extendable by subclassing

implementation

     // .h file 
  
     class Singleton {
     public:
  	static Singleton instance();
     protected:  limit access
  	Singleton();
     private:
  	static Singleton* _instance;
     };
  
  
     // .c file
  
     Singleton* Singleton::_instance = 0;
  
     Singleton* Singleton::instance() {
  	if (_instance == 0)
  		_instance = new Singleton();
  	return _instance;
  	}

consequences

coordinate access to a single instance
reduced namespace
permit refinement
permit variable number of instances

etcetera

see GOF

prototype

specify kinds of objects to create using a prototypical instance and create by copying this prototype

motivation

flexibility, reduce number of classes

applicability

when classes to instantiate are specified at runtime
to avoid building a class hierarchy of factories
to reduce static dependencies

participants

Prototype, ConcretePrototype, Client

consequences

adding and removing product types at runtime
specifying new objects by varying value/structure
reduced subclassing
configure an application with classes dynamically see kit.h and dv/tk/kit.c

AbstractFactory versus Prototype

pattern(s) / matrix / model(s) / resource(s)

structural patterns

are concerned with how classes and objects are composed to form larger structures

Pattern Alias Remarks

language mechanisms

inheritance -- class
delegation -- object

adaptor vs bridge

wrapper

adaptor -- resolves inconsistencies between interfaces
bridge -- relates abstraction to ... implementation

Composite vs Decorator vs Proxy

recursive composition

Composite represents structure
Decorator adds responsibilities
Proxy regulates access

pattern(s) / matrix / model(s) / resource(s)

behavioral patterns

communication

deal with algorithms and the assignment of responsibilities between objects

class

template method -- the skeleton of an algorithm
interpreter -- to evaluate expressions

object

composition

mediator -- provides indirection for loose coupling
chain of responsibility -- connect objects to interact
observer -- to handle dependencies

encapsulating behavior

objectify!

strategy -- algorithm
command -- request
state -- object state -> behavioral change
visitor -- to extract behavior from class
iterator -- access and traversal

observer

one-to-many dependencies and notification

structure

consequences

abstract coupling between subject and observer
support for broadcast
deals with unexpected updates

implementation

mapping subjects to observers
observing more than one subject?
who triggers the update - subject or client of subject
dangling references to subject
consistency of subject (before notification)
adding observer-specific update protocols (push / pull)
specifying modifications of interest (aspects)
how to encapsulate update semantics

[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

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design patterns

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creational patterns

factory

Example

also known as kit

participants

consequences

implementation

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factory method

also know as

motivation

applicability

structure

participants

consequences

related

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singleton

applicability

implementation

limit access

consequences

etcetera

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prototype

motivation

applicability

participants

consequences

related

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structural patterns

structural patterns

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language mechanisms

adaptor vs bridge

Composite vs Decorator vs Proxy

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behavioral patterns

behavioral patterns

class

object

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encapsulating behavior

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observer

structure

consequences

implementation

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