applying software design principles in practice
DESCRIPTION
How to develop high quality software? What are the key/fundamental principles for software design? What is the relationship between principles, bad smells, design patterns, and refactoring? This presentation answers all this and more. Don't miss it!TRANSCRIPT
How to apply design principles in practice?
Ganesh Samarthyam!Consultant, ZineMind [email protected]
“Applying design principles is the key to creating high-quality software!”
Architectural principles: !Axis, symmetry, rhythm, datum, hierarchy, transformation
Technology changes fast => FOMO
Often frustrating to develop quality software!
There must be a better way!“Here is Edward Bear,
coming downstairs now, bump, bump, bump,
on the back of his head, behind Christopher Robin.
It is, as far as ... !
It is, as far as he knows, the only way of coming downstairs,
but sometimes he feels that there really is another way,
if only he could stop bumping for a moment and think of it!”
!- A.A. Milne
Think, think, think!
Focus on software design is the key!
Real scenario #1Initial design
Real scenario #1
❖ How will you refactor such that:!
❖ A specific DES, AES, TDES, … can be “plugged” at runtime?!
❖ Reuse these algorithms in new contexts? !
❖ Easily add support for new algorithms in Encryption? !
Next change: smelly design
Time to refactor!Three strikes and you
refactor
Martin Fowler
Potential solution #1?Broken
hierarchy!
Yuck! !Your solution smells
Potential solution #2?Algorithms not
reusable!
Hmm, can be better. !Better luck next time…
Potential solution #3?
Wow!!What a nice solution :)
Can you identify the pattern?
You’re right: Its Strategy pattern!
Real scenario #2
Initial design
Real scenario #2
How to add support for new content types and/or algorithms?
Yuck! !This design smells
How about this solution?
Wow!!What a nice solution :)
Can you identify the pattern structure?
You’re right: Its Bridge pattern!
Wait, what principle did we apply?
Open Closed Principle (OCP)
Bertrand Meyer
Software entities should be open for extension, but closed for modification
Variation Encapsulation Principle (VEP)
Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides
Encapsulate the concept that varies
Fundamental principle: Encapsulation
The principle of encapsulation advocates separation of concerns and!information hiding through techniques such as hiding implementation!
details of abstractions and hiding variations
Enabling techniques for encapsulation
Other fundamental principles?
Principles*
Abstrac/on*
Encapsula/on*
Modulariza/on*
Hierarchy*
Applying principles in practice
EncapsulationViolating!
encapsulationAdherence to !encapsulation
Applying !encapsulation
Applying principles in practice
PrincipleViolating!principles
Adherence to !principles
Refactoring
Bad design !(with smells)
Good design (with patterns)
Design determines qualities
Understandability Changeability Extensibility
Reusability Testability Reliability
DESIGNimpacts
impactsimpacts
“Applying design principles is the key to creating high-quality software!”
Architectural principles: !Axis, symmetry, rhythm, datum, hierarchy, transformation
Presentation sourceForewords by
Grady Booch and Dr. Stephane Ducasse
What are your takeaways?
Image/video credits❖ http://en.wikipedia.org/wiki/Fear_of_missing_out!❖ http://lesliejanemoran.blogspot.in/2010_05_01_archive.html!❖ http://javra.eu/wp-content/uploads/2013/07/angry_laptop2.jpg!❖ https://www.youtube.com/watch?v=5R8XHrfJkeg!❖ http://womenworld.org/image/052013/31/113745161.jpg!❖ http://www.fantom-xp.com/wallpapers/33/I'm_not_sure.jpg!❖ https://www.flickr.com/photos/31457017@N00/453784086 !❖ https://www.gradtouch.com/uploads/images/question3.jpg!❖ http://gurujohn.files.wordpress.com/2008/06/bookcover0001.jpg !❖ http://upload.wikimedia.org/wikipedia/commons/d/d5/Martin_Fowler_-_Swipe_Conference_2012.jpg!❖ http://www.codeproject.com/KB/architecture/csdespat_2/dpcs_br.gif !❖ http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Bertrand_Meyer_IMG_2481.jpg/440px-
Bertrand_Meyer_IMG_2481.jpg !❖ http://takeji-soft.up.n.seesaa.net/takeji-soft/image/GOF-OOPLSA-94-Color-75.jpg?d=a0 !❖ https://developer.apple.com/library/ios/documentation/cocoa/Conceptual/OOP_ObjC/Art/watchcalls_35.gif!❖ http://www.pluspack.com/files/billeder/Newsletter/25/takeaway_bag.png !❖ http://cdn1.tnwcdn.com/wp-content/blogs.dir/1/files/2013/03/design.jpg
