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patterns
Methods do not provide the intuiton and the direct access
to solutions that work in real life.
Design Patterns
are the jewels, the cristals of Object Oriented Design ...
Motivation
Take for example a document processing system ...
- material - words, images, tables
- formatting, layout
- online presentation and editing tool
Managing composites
Problem: very many items
Solution: flyweight class
Managing layout and formatting
Problem: many algorithms
Solution: composer (strategy) class
Display item with attributes
Problem: non-uniform attributes
Solution: embed and hide attributes
Develop multi-platform tools (1)
Problem: different window toolkits
Solution: employ platform-specific factories
Develop multi-platform tools (2)
Problem: offer uniform widget hierarchy
Solution: separate interface from implementation
Provide rich functionality
Problem: support commands with undo
Solution: abstract from specific commands
observer
Observer
one-to-many dependencies and notification
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)
_
(C) Æliens 04/09/2009
You may not copy or print any of this material without explicit permission of the author or the publisher. In case of other copyright issues, contact the author.