1. Course information Old exam Resit Report Result and walkthrough
30 november,
Report
Should be under way‏

2. Helt irrelevant för kursen
First Lego League
5 studenter sökes som domare
Programmering av legorobotar
10-15-åringar
7 november
Molkoms högstadium (Nyed)
100:-/h

3. W7 – Processes and Principles
TDD, Pair Programming, Stand-ups
SRP, OCP, LSP, DIP, ISP

4. TDD – Uncle Bob’s 3 laws

5. TDD - FIRST

6. TDD – Red-Green-Refactor

7. Pair Programming Always code in pairs Switch driver/co-driver
Switch pairs
Knowledge spread

8. Stand-up meetings Short and time-boxed What have I done What will I do
Problems

9. SRP (Single Responsibility Principle)‏
A class should only have one reason to change
Cohesion
How focused a class is

10. Example - RBS
Who should know the price of a room/catering item/piece of equipment?
Domain vs storage

11. OCP (Open-Closed Principle)‏
Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification
Existing clients should not have to care about future improvements
Future improvements should be possible
Abstration is the key
Refactoring

12. OCP (cont'd)‏
"Open For Extension" - It is possible to extend the behavior of the module as the requirements of the application change (i.e. change the behavior of the module).
"Closed For Modification" - Extending the behavior of the module does not result in the changing of the source code or binary code of the module itself.

13. OCP - example

14. OCP - Bertrand Meyer
“A module will be said to be open if is still available for extension
For example, it should be possible to add fields to the data structures it contains, or new elements to the set of functions it performs”
“A module will be said to be closed if is available for use by other modules
This assumes that the module has been given a well-defined, stable description (the interface...)”

15. LSP (Liskov Substitution Principle)‏
“What is wanted is something like the following substitution property: If for each object o1 of type S there is an object o2 of type T such that for all programs P defined in terms of T, the behavior of P is unchanged when o1 is substituted for o2, then S is a subtype of T. [Liskov88]“
Subtypes must be substitutable for their base types [Uncle Bob]

16. LSP - example public class Rectangle { protected int _width;
protected int _height;
public int Width
get { return _width; } }
public int Height
get { return _height; }
public virtual void SetWidth(int width)‏
_width = width;
public virtual void SetHeight(int height)‏
_height = height;
public class Square: Rectangle {
public override void SetWidth(int width)‏
_width = width;
_height = width; }
public override void SetHeight(int height)‏
_height = height;
_width = _height;

17. LSP – example (cont'd)‏ r.Width = 5; r.Height = 2;
[TestFixture]
public class RectangleTests {
[Test]
public void AreaOfRectangle()‏
Rectangle r = new Square();
r.Width = 5;
r.Height = 2;
// Will Fail - r is a square and sets
// width and height equal to each other.
Assert.IsEqual(r.Width * r.Height,10); }

18. DIP (Dependency-Inversion Principle)‏
Making your applications loosely coupled by not depending on concrete classes when appropriate, but abstractions
High-level modules should not depend on low- level modules. Both should depend on abstractions.
Abstractions should not depend on details. Details should depend on abstractions.

19. DIP - Good, bad, ugly

20. DIP – good for reuse Low-level modules are already being reused
Buttons and other graphical objects
Lists and other containers
High-level modules are harder to reuse
DIP helps reusing higher modules
Decoupling from details

21. ISP (Interface Segregation Principle)‏
Clients should not be forced to depend on methods that they do not use
Related to cohesion

22. ISP - Example ATM Deposit Withdraw Transfer
3 different uses of the system
3 different interfaces
You don't want to see stuff with no relevance

23. ISP – Example 2 Name Personal number Income IRS Name Pnr Grades Kau
Artist