Design Principles Incremental Design, Single Responsibility, and Dependency Inversion Michael Denomy September 19, 2013 Launch Academy, Boston MA Sunday, September 22, 13
Design Principles - Michael Denomy at Launch Academy
Jun 20, 2015
In this talk I gave at Launch Academy, a developer boot-camp in Boston, I go over some key design principles. I introduce the SOLID design principles, focusing on Single Responsibility and Dependency Inversion, as well as talk about Incremental Design
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Design PrinciplesIncremental Design, Single Responsibility,
and Dependency Inversion
Michael DenomySeptember 19, 2013Launch Academy, Boston MA
Sunday, September 22, 13
About MeTech Lead at Cyrus Innovation
Passionate about Agile and XPPairingTDDIncremental Design
Contact Me@mdenomy on Twitter and GitHubhttp://mdenomy.wordpress.com/
Sunday, September 22, 13
SOLID Design PrinciplesSet of principles identified by Bob Martin, aka Uncle Bob- Somewhere in the 1995-2000 timeframe- Uncle Bob has some strong opinions on
software, you should check them out
Sunday, September 22, 13
SOLID Design PrinciplesS Single ResponsibilityO Open-Closed L Liskov SubstitutionI Interface SegregationD Dependency Inversion not Dependency Injection
Sunday, September 22, 13
SOLID Design PrinciplesS Single ResponsibilityD Dependency Inversion not Dependency Injection
That’s plenty for today
Sunday, September 22, 13
Single ResponsibilityOfficial Definition- A class should have only one reason to
change
What It Means To You- Keep your classes small- Don’t mix responsibilities- CheckingAccount manages balance and
calculates fees
Sunday, September 22, 13
Dependency InversionOfficial Definition- Depend on abstractions not concretions
What It Means To You- Your class should not know the details of its
dependencies, just the interfaces- Ideally both ends of the dependency
relationship deal with abstractions, i.e. interfaces- Dependency injection is a way to implement
dependency inversion
Sunday, September 22, 13
Incremental DesignAlways Be DesigningPay attention to “code smells”The simplest thing that worksRed-Green-Refactor
not Red-Green-Red-Green-Red-Green-Refactor-Refactor-Refactor-Refactor-Refactor
You will never know less than you know now
- Sandi Metz, Practical OOD in Ruby (POODR)
Sunday, September 22, 13
Let’s Look at Some CodeReally Simple Example of a CheckingAccount
Work in small increments
Learn about the problem as we go
Listen for code smells
https://github.com/mdenomy/intro-design-workshopNote:Readme contains design thoughts as I go
Sunday, September 22, 13
Take-AwaysWork small
Pay attention to design trade-offs, technical debt, and naming
Be students of your craftProcesses, frameworks, tools, everything
Challenge your assumptionsJust cause it’s the “right” way today...
Sunday, September 22, 13
ReferencesBob Martin (Uncle Bob) on SOLIDhttp://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
Sandi Metz - SOLID Talk at GORUCOhttp://www.confreaks.com/videos/240-goruco2009-solid-object-oriented-design
Derick Bailey - Los Techieshttp://lostechies.com/derickbailey/2011/09/22/dependency-injection-is-not-the-same-as-the-dependency-inversion-principle/
James Shore - Art of Agilehttp://www.jamesshore.com/Agile-Book/incremental_design.html
Sunday, September 22, 13
Thank YouQ&A
Sunday, September 22, 13
Design PrinciplesIncremental Design, Single Responsibility,
and Dependency Inversion
Michael DenomySeptember 19, 2013Launch Academy
Sunday, September 22, 13
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