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Coding Defines RealityCode Mania #101
@varokas BIGBEARS.
Design
Design
Creating Solutions based on
1. Requirements
2. Desired Properties
• Available
• Reliable
• Performance
• Maintainable
• Reusable
• Usable
Design is very easyKnowing what you want is very hard
Christopher Alexander
Christopher Alexander
Principles of Emergent Design
Contextual Force
Force
Force
Force
Force
Force
Force
Force ForceDesign
Force Force
Force
Force
Force
Force
Force
Force
Design
–Johnny Appleseed
“Type a quote here.” Force Force
Force
Force
Force
Force
Force
Force
Design
Feel the force!Do not put in one that does not exist
Patterns
Design Patterns
Patterns
•
“The Pattern is in the problem”
–Johnny Appleseed
“Type a quote here.”
Pattern
Problem
“Don't Solve the Problem. Discover the Pattern”
Emergent Design
Change from Create Solutions
to Discover Solutions
Discovering Techniques
• Code Properties Analysis
• Commonality Variability Analysis
• Programming by Intention
• Tests (TDD)
CommonalityVariabilityAnalysis
CommonalityVariabilityAnalysis
• What is in Common?
• What Varies?
• Under a certain Context of Use
CVA Example (non-software)
CVA Exercise (Pen-Pencil)
Pen
• write with ink • can't erase
Pencil
• write with lead • can erase
?
• write • cylinder • can put in a box • breakable • ....
CVA Exercise (Pen-Pencil)
Pen
• write with ink• can't erase
Pencil
• write with lead• can erase
WritingTool
• write• cylinder • can put in a box
WritingUser
CVA Exercise (Pen-Pencil)
Pen
write() { //inkImpl}
Pencil
write() { //leadImpl}
WritingTool
write()
WritingUser
CVA Exercise (Pen-Pencil)
Penwrite() { //inkImpl}
Pencil
write() { //leadImpl}
WritingTool
write()
interface WritingTool { def write() }
class Pen extends WritingTool { def write() { //ink impl } }
class Pencil extends WritingTool { def write() { //lead impl } }
CVA Exercise (Pen-Pencil)
Pen
write() { //inkImpl}
Pencil
write() { //leadImpl}
WritingTool
write()
WritingUser
CVA Exercise (2)
• There are two types of shape (Circle, Square)
• There are two types of writer (Pen, Pencil)
• Each shape can print itself on different writers
CVA Exercise (2)
Pen
write() { //inkImpl}
Pencil
write() { //leadImpl}
Writer
write() • There are two types of shape (Circle, Square)
• There are two types of writer (Pen, Pencil)
• Each shape can print itself on different writers
CVA Exercise (2)
Pen
write() { //inkImpl}
Pencil
write() { //leadImpl}
Writer
write()
Square
Shape
• There are two types of shape (Circle, Square)
Circle
CVA Exercise (2)
Pen
write() { //inkImpl}
Pencil
write() { //leadImpl}
Writer
write()
Square
Shape
print()
• Each shape can print itself on different writers
Circle
Programming by Intention
• "So what do we want to do"?
Perspective
• Conceptual
• Specification
• Implementation
Starbucks
• Create a software for cashier and barista
• A program accepts order from user
• Retrieve cost based on the order
• A program shows the barista what to do
Starbucks• A program creates
order from user
• Retrieve cost based on the order
• A program shows the barista what to do
order = user.createOrder()
cost = order.getCost()
inst = order.whatToDo()
Starbucks
• Select Size of cup (S,M,L)
• (S) Cup -> Coffee
• (M) Cup -> Coffee x 2
• (L) Cup -> Coffee x 3
• S = 100, M = 120, L = 150
order = user.createOrder() { selectSize() }
cost = order.getCost() inst = order.whatToDo()
Starbucks
• Select Size of cup (S,M,L)
• (S) Cup -> Coffee
• (M) Cup -> Coffee x 2
• (L) Cup -> Coffee x 3
• S = 100, M = 120, L = 150
M
coffee() { //2}price() { //120}
Cup
coffee()price()
S
coffee() { //1}price() { //100}
L
coffee() { //3}price() { //150}
Starbucks
order = user.createOrder() { selectSize() }
cost = order.getCost() { order.getCup().getPrice() } M
coffee() { //2}price() { //120}
Cup
coffee()price()
S
coffee() { //1}price() { //100}
L
coffee() { //3}price() { //150}
Order
Closing Thoughts
When does design starts?When does it end?
`
http://askmissa.com/wp-content/uploads/2011/10/photo5.jpg
http://en.wikipedia.org/wiki/File:Space_Needle_2011-07-04.jpg
http://sherrlock.files.wordpress.com/2011/06/space-needle-elevationsweb1.jpg?w=500&h=540
Happy Coding! (Designing)
Other slides
Starbucks (v2)• Select Coffee Type (Hot/Cold) [ cold serve with ice ]
• Select Size of cup (S,M,L)
• (S) Cup -> Coffee
• (M) Cup -> Coffee x 2
• (L) Cup -> Coffee x 3
• S = 100, M = 120, L = 150, Hot/Cold = Same price
Starbucks (v3)• Select Coffee Type (Hot/Cold) [ cold serve with ice ]
• Americano [ Coffee + Water ]
• Cappuccino [ Coffee + Milk + Whip the milk ]
• Latte [ Coffee + Milk ]
• Select Size of cup (S,M,L)
• (S) Cup -> Coffee
• (M) Cup -> Coffee x 2
• (L) Cup -> Coffee x 3
• S = 100, M = 120, L = 150, Hot/Cold = Same price, Latte +10, Cappucino + 20
