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 2012. However, the demonstrated patterns and practice can be applied to every other programming language too.
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Clean Code I - Design Patterns and Best Practices at SoCal Code Camp San Diego (07/27/2013)
1. Clean Code I
San Diego, July 27th, 2013
SolCal
Code Camp
Design Patterns
and Best Practices
2. Theo Jungeblut
• Engineering manager & lead by day
at AppDynamics in San Francisco
• Coder & software craftsman by night
• Architects decoupled solutions
tailored to business needs & crafts
maintainable code to last
• Worked in healthcare and factory
automation, building mission critical
applications, framework & platforms
• Degree in Software Engineering
and Network Communications
• Enjoys cycling, running and eating
theo@designitright.net
www.designitright.net
3. Rate Session & Win a Shirt
http://www.speakerrate.com/theoj
4. Where to get the Slides
http://www.slideshare.net/theojungeblut
11. 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.”
14. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 1st Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
16. KISS-Principle – “Keep It Simple Stupid”
http://blogs.smarter.com/blogs/Lego%20Brick.jpg
by Kelly Johnson
17. 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
18. Chaos build from simplicity
Graphic by Nathan Sawaya courtesy of brickartist.com
20. 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();
}
}
21. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 1st Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
22. Clean Code Developer – 2nd Iteration
by 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/
27. 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/Separati
on_of_Concerns
28. 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)
{}
}
30. Clean Code Developer – 2nd Iteration
by 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/
31. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 3rd Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
33. “.. 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
34. 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)
{}
}
36. “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
38. 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
40. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 3rd Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
41. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 4th Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
43. 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
45. “
• 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
46. Single Responsibility Principle
Open/Closed Principle
Liskov Substitution Principle
Interface Segregation Principle
Dependency Inversion Principle
S
O
L
I
D
Robert C Martin: http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
47. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 4th Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
48. Graphic by Michael Hönnig http://michael.hoennig.de/2009/08/08/clean-code-developer-ccd/
Clean Code Developer – 5th Iteration
by Ralf Westphal & Stefan Lieser – http://www.clean-code-developer.de
49. 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!)
50. Downloads,
Feedback & Comments:
Q & A
Graphic by Nathan Sawaya courtesy of brickartist.com
theo@designitright.net
www.designitright.net
www.speakerrate.com/theoj