[.] DejaVU Online: -- The OO Lectures

[.] - [up] [top] - [I] [II] [III] [IV] - [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] - [A] [R]

Behavioral Patterns

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

slide: Behavioral Patterns

Encapsulating behavior

objectify!

Strategy -- algorithm
Command -- request
State -- object state -> behavioral change
Visitor -- to extract behavior from class
Iterator -- access and traversal

slide: Encapsulating behavior

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

slide: Observer Pattern

[.] - [up] [top] - [I] [II] [III] [IV] - [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] - [A] [R]

Hush Online Technology

hush@cs.vu.nl
02/15/00