scott cate (@scottcate) clouddb.com session code: dpr401
TRANSCRIPT
Patterns for the Rest of UsScott Cate (@ScottCate)CloudDB.comSession Code: DPR401
Design Patterns for the Rest of Us! DPR401Patterns Patterns Patterns. You hear about them everywhere.
We're told to use them and call them by names, as if the pattern is a colleague of ours. Hey, did you see the {Fill In Blank} Pattern in the demo this morning?
If you feel left out in conversations where Pattern buzzwords are thrown around, this session is for you.
This session introduces Patterns with imagery, code, terms, and fun and games to help you better understand and remember pattern usage.
Design PatternsTarget audience for this talk
You know the language very wellYou are an advanced programmerBUT …..
It’s difficult to explain what your code doesOthers tell you your code is hard to readYour code is buggy / hard to maintainChanging something little causes other unknownsYOU ARE NOT ALONE!IT IS HARD TO ADMIT THIS!
The Life Cycle of Bad Source CodeRewrite == expensive
The original author is goneThe code is hard to readHard to understand functionalityCause to rewrite / replaceBetter code with patternsProprietary == EXPENSIVE!
Where We Started! (Most of us)
OO Spaghetti CodeNot my code, my code is good to me
Is that because you wrote it?It’s in your head so you understand itIs the code hard to read / explain?
Easy to get started with sloppy code but…It’s hard to add functionality laterIt’s hard to make core changes later
How We’ve Cleaned Up Our Code (Most of us)
Developing by Contract The unknown neighbor
Handling Change Requests Should be this easy
Building Blocks
What is a Design Pattern?(This is a legit question)
No, it’s not a scary monsterProven Logical TechniquesTech communities agree on patterns
(it’s hard to get people to agree)Common Vocabulary
Easy to understand / inherit / readJust a term – not a golden solution
GOF: 3 Design Pattern CategoriesDozens of more categories, these are GOF
CreationHow, Where, When, Why do you instantiate objects?GOF: Factories, Builder, Prototype, Singleton
StructuralChange, Migrate, Add to, Copy, Split, Move objectsGOF: Adapter, Bridge, Composite, Decorator, Façade, Flyweight, Proxy
BehavioralPassing around, working on, alter, add functionality to objectsCommand, Chain of Responsibility, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template, Visitor
Commonly Used Design Patterns!Observer Pattern – Start nice and easy
demo / write code
Commonly used Design Patterns!Singleton Pattern – Very common / Easy to write
demo / write code
Commonly Used Design Patterns!Factory Pattern – Delegate “New”ing objects
demo / write code
Commonly Used Design Patterns!Command (AKA Action) Pattern – Store, Queue, Execute
demo / write code
Commonly Used Design Patterns!Template – Delegate base functionality
demo / write code
Commonly Used Design Patterns!State Pattern – Delegate action based on state
demo / write code
Commonly Used Design Patterns!Strategy Pattern – Algorithms / Single or Multi Pass
demo / write code
Anti PatternsSquare Pegs / Round Holes
Don’t use a pattern just becauseDon’t over engineerDon’t make fun of othersDon’t overuse a pattern
If every class uses the same patternit’s probably over used.This is an easy trap to fall into.
Special ThanksBrainstorm + session guidance
Jeffrey PalermoGlenn BlockWard BellJames AveryPaul GlavichJeff Widmer
Recommended Reading(where to learn more)
Elements of Reusable Object-Oriented SoftwareCommonly known as “The Gang of Four”
Martin Fowler’s PoEAAPatterns of Enterprise Application Architecture
O’Reilly: Head First Design PatternsJoshua Kerievsky
Refactoring to PatternsDoFactory.com
Track Resources
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