clean code part i - design patterns at socal code camp
DESCRIPTION
Within this session you will learn and/or refresh the most important architectural design pattern and best practices to write better code. These patterns and practices build the foundation for writing maintainable application. More advances techniques like Inversion of Control and Dependency Injection are discussed in detail in the 2nd Clean Code presentation. All 3 Clean Code presentations provide great value by themselves, but taken together are designed to offer a holistic approach to successful software creation. This first session creates the foundation for the 2nd Clean Code presentation on Dependency Injection, as it explains expected base knowledge. Why writing Clean Code makes us more efficient Over the lifetime of a product, maintaining the product is actually one - if not the most - expensive area(s) of the overall product costs. Writing clean code can significantly lower these costs. However, writing clean code also makes you more efficient during the initial development time and results in more stable code. You will be presented design patterns and best practices which will make you write better and more easily maintainable code, seeing code in a holistic way. You will learn how to apply them by using an existing implementation as the starting point of the presentation. Finally, patterns & practices benefits are explained. This presentation is based on C# and Visual Studio 2010. However, the demonstrated patterns and practice can be applied to every other programming language too.TRANSCRIPT
Clean Code IDesign Patterns
and Best PracticesSan Diego, June 24rd 2012
SolCalCodeCamp
Theo Jungeblut• Senior Software Developer at
AppDynamics in San Francisco
• architects decoupled solutions tailored to business needs and crafts maintainable code to last
• worked in healthcare and factory automation, building mission critical applications, framework & platforms for 8+ years
• degree in Software Engineeringand Network Communications
• enjoys cycling, running and [email protected]
www.designitright.net www.speakerrate.com/theoj
Overview• Why Clean Code• Clean Code Developer Initiative • Principles and Practices• Code Comparison• Q&A
Does writing Clean Code make us more efficient?
The only valid Measurement of Code Quality
What is Clean Code?
Clean Code is maintainable
Source code must be:• readable & well structured• extensible• testable
Software Engineering
vs. Craftsmanship
Software Engineering
ANDCraftsmanship
The “Must Read”-Book(s)by Robert C Martin
A Handbook of Agile Software Craftsmanship
“Even bad code can function. But if code isn’t clean, it can bring a development organization to its knees.”
Code Maintainability *
Principles Patterns Containers
Why? How? What?
Extensibility Clean Code Tool reuse
* from: Mark Seemann’s “Dependency Injection in .NET” presentation Bay.NET 05/2011
Clean Code Developer
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 1st Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Keep it simple, stupid(KISS)
KISS-Principle – “Keep It Simple Stupid”
http://blogs.smarter.com/blogs/Lego%20Brick.jpg
by Kelly Johnson
The Power of Simplicity
http://www.geekalerts.com/lego-iphone/
Graphic by Nathan Sawaya courtesy of brickartist.com
Graphic by Nathan Sawaya courtesy of brickartist.com
Chaos build from simplicity
Graphic by Nathan Sawaya courtesy of brickartist.com
Don’t repeat yourself(DRY)
Don’t repeat yourself (DRY)by Andy Hunt and Dave Thomas in their book “The Pragmatic Programmer”
// Code Copy and Paste Method public Class Person { public string FirstName { get; set;} public string LastName { get; set;} public Person(Person person) { this.FirstName = string.IsNullOrEmpty(person.FirstName)
? string.Empty : (string) person.FirstName.Clone();
this.LastName = string.IsNullOrEmpty(person.LastName) ? string.Empty : (string) person.LastName.Clone();
}
public object Clone() { return new Person(this); }}
// DRY Method public Class Person { public string FirstName { get; set;} public string LastName { get; set;} public Person(Person person) { this.FirstName = person.FirstName.CloneSecured(); this.LastName = person.LastName.CloneSecured(); }
public object Clone() { return new Person(this); }}
public static class StringExtension { public static string CloneSecured(this string original) { return string.IsNullOrEmpty(original) ? string.Empty : (string)original.Clone(); } }
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 1st Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Clean Code Developer – 2nd Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Separation of Concerns (SoC)
Single Responsibility Principle
(SRP)
http://www.technicopedia.com/8865.html
The Product
http://www.technicopedia.com/8865.html
Component / Service
http://technicbricks.blogspot.com/2009/06/tbs-techpoll-12-results-2009-1st.html
Class, Struct, Enum etc.
Separation of Concerns (SoC)
• “In computer science, separation of concerns (SoC) is the process of separating a computer program into distinct features that overlap in functionality as little as possible.
•A concern is any piece of interest or focus in a program. Typically, concerns are synonymous with features or behaviors. “
probably by Edsger W. Dijkstra in 1974
http://en.wikipedia.org/wiki/Separation_of_Concerns
Single Responsibility Principle (SRP)
“Every object should have a single responsibility, and that responsibility should be entirely encapsulated by the class.”
by Robert C Martin
http://www.ericalbrecht.com
http://en.wikipedia.org/wiki/Single_responsibility_principle
public class Logger : ILogger{ public Logger(ILoggingSink loggingSink) {} public void Log(string message) {}}
Read, Read, Read
Clean Code Developer – 2nd Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
SoftwareCraftsmanship
San Diego, June 23rd 2012
SolCalCodeCamp
WarningAdvertising
Clean Code III
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 3rd Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Information Hiding Principle(IHP)
“.. information hiding is the principle of segregation of the design decisions on a computer program that are most likely to change, ..”
Information Hiding Principle (IHP)by David Parnas (1972)
http://en.wikipedia.org/wiki/Information_hiding
Interfaces / Contracts
public interface ILogger{ void Log(string message);}
• Decouple Usage and Implementation through introduction of a contract• Allows to replace implementation without changing the consumer
public class Logger : ILogger{ public Logger(ILoggingSink loggingSink) {} public void Log(string message) {}}
Liskov Substitution Principle(LSP)
“Liskov’s notion of a behavioral subtype defines a notion of substitutability for mutable objects”
Liskov Substitution Principle (LSP)by Barbara Liskov, Jannette Wing (1994)
http://en.wikipedia.org/wiki/Liskov_substitution_principle
Dependency Inversion Principle(DIP)
Dependency Inversion Principle (DIP)
• “High-level modules should not depend on low-level modules. Both should depend on abstractions.
• Abstractions should not depend upon details. Details should depend upon abstractions.”
http://en.wikipedia.org/wiki/Dependency_inversion_principle
by Robert C. Martin
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 3rd Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 4th Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Open Closed Principle(OCP)
An implementation is open for extension but closed for modification
Open/Closed Principle (OCP)by Bertrand Meyer (1988)
http://en.wikipedia.org/wiki/Open/closed_principle
Law of Demeter(LoD)
“• Each unit should have only limited knowledge
about other units: only units “closely” related to the current unit.
• Each unit should only talk to its friends; don’t talk to strangers
• Only talk to your immediate friends.”
Law of Demeter (LoD)Northeastern University (1987)
http://en.wikipedia.org/wiki/Law_Of_Demeter
Single Responsibility Principle
Open/Closed Principle
Liskov Substitution Principle
Interface Segregation Principle
Dependency Inversion Principle
SOLID
Robert C Martin: http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 4th Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Silicon Valley Code Camp Oct. 6th – 7th
http://www.siliconvalley-codecamp.com
Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 5th Iterationby Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
Summary Clean Code Maintainability is achieved through:
• Readability (Coding Guidelines)
• Simplification and Specialization (KISS, SoC, SRP, OCP, )
• Decoupling (LSP, DIP, IHP, Contracts, LoD, CoP, IoC or SOA)
• Avoiding Code Bloat (DRY, YAGNI)
• Quality through Testability (all of them!)
Downloads, Feedback & Comments:
Q & A
Graphic by Nathan Sawaya courtesy of brickartist.com
[email protected] www.speakerrate.com/theoj
References… http://clean-code-developer.comhttp://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOodhttp://www.manning.com/seemann/http://en.wikipedia.org/wiki/Keep_it_simple_stupidhttp://picocontainer.org/patterns.htmlhttp://en.wikipedia.org/wiki/Separation_of_concernshttp://en.wikipedia.org/wiki/Single_responsibility_principlehttp://en.wikipedia.org/wiki/Information_hidinghttp://en.wikipedia.org/wiki/Liskov_substitution_principlehttp://en.wikipedia.org/wiki/Dependency_inversion_principlehttp://en.wikipedia.org/wiki/Open/closed_principlehttp://en.wikipedia.org/wiki/Law_Of_Demeterhttp://en.wikipedia.org/wiki/Don't_repeat_yourselfhttp://en.wikipedia.org/wiki/You_ain't_gonna_need_ithttp://en.wikipedia.org/wiki/Component-oriented_programminghttp://en.wikipedia.org/wiki/Service-oriented_architecturehttp://www.martinfowler.com/articles/injection.htmlhttp://www.codeproject.com/KB/aspnet/IOCDI.aspxhttp://msdn.microsoft.com/en-us/magazine/cc163739.aspxhttp://msdn.microsoft.com/en-us/library/ff650320.aspxhttp://msdn.microsoft.com/en-us/library/aa973811.aspxhttp://msdn.microsoft.com/en-us/library/ff647976.aspxhttp://msdn.microsoft.com/en-us/library/cc707845.aspxhttp://msdn.microsoft.com/en-us/library/bb833022.aspxhttp://unity.codeplex.com/http://www.idesign.net/idesign/DesktopDefault.aspx?tabindex=5&tabid=11
… more ReferencesResharperhttp://www.jetbrains.com/resharper/
FxCop / Code Analysis http://msdn.microsoft.com/en-us/library/bb429476(VS.80).aspxhttp://blogs.msdn.com/b/codeanalysis/http://www.binarycoder.net/fxcop/index.html
Code Contractshttp://msdn.microsoft.com/en-us/devlabs/dd491992http://research.microsoft.com/en-us/projects/contracts/
Pex & Molehttp://research.microsoft.com/en-us/projects/pex/
StyleCophttp://stylecop.codeplex.com/
Ghostdoc http://submain.com/products/ghostdoc.aspx
Spellcheckerhttp://visualstudiogallery.msdn.microsoft.com/7c8341f1-ebac-40c8-92c2-476db8d523ce// Lego (trademarked in capitals as LEGO)
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