OOPs Development with Scala
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Here is one way to model the parking lot system using object-oriented design principles: 1. ParkingSpot class - Properties: id, type (regular, handicapped, compact), occupied - Methods: occupy(), vacate() 2. ParkingLot class - Properties: spots (list of ParkingSpot), currentOccupancy - Methods: - findSpotForRegularCar() - findSpotForHandicappedCar() - findSpotForCompactCar() - isFull() - isEmpty() 3. ValetParking class - Property: currentSpot - Methods: - parkCar() - retrieveCar() 4. Car class -
![case class Bank(id:Int, name:String)
case class Check(number:Int, bank:Bank)
class FastProcessor {
def process(checks:List[Check]) = checks foreach (check => sendEmail)
def sendEmail = println("Email sent")
}
val citibank = new Bank(1, "Citibank") //> citibank :
com.baml.ooad.Bank = Bank(1,Citibank)
(new FastProcessor).process(List(new Check(1,citibank), new Check(2,citibank)))
//> Email sent
//| Email sent](https://image.slidesharecdn.com/baml-oops-121216113235-phpapp01/85/OOPs-Development-with-Scala-20-320.jpg)
![case class Bank(id:Int, name:String)
case class Check(number:Int, bank:Bank)
class FastProcessor {
def process(checks:List[Check]) = checks foreach (check => if
(check.bank.name=="Citibank") sendEmail else sendFax)
def sendEmail = println("Email sent")
def sendFax = println("Fax sent")
}
val citibank = new Bank(1, "Citibank") //
val bankOfAmerica = new Bank(2, "BoA")
//
val citibankCheckList = List(new Check(1,citibank), new Check(2,citibank))
val bankOfAmericaCheckList = List(new Check(1,bankOfAmerica), new
Check(2,bankOfAmerica))
(new FastProcessor).process(citibankCheckList ::: bankOfAmericaCheckList)
//> Email sent
//| Email sent
//| Fax sent
//| Fax sent](https://image.slidesharecdn.com/baml-oops-121216113235-phpapp01/85/OOPs-Development-with-Scala-23-320.jpg)
![class FastProcessor {
def process(checks: List[Check]) = checks foreach (check =>
check.bank.process(check))
}
val citibankCheckList = List(new Check(1, CitiBank), new Check(2,
CitiBank))
val bankOfAmericaCheckList = List(new Check(1, BankOfAmerica), new
Check(2, BankOfAmerica))
val hdfcCheckList = List(new Check(1, HDFC))
(new FastProcessor).process(citibankCheckList :::
bankOfAmericaCheckList ::: hdfcCheckList)
//> Email sent
//| Email sent
//| Fax sent
//| Fax sent
//| Fax sent
//| Email sent](https://image.slidesharecdn.com/baml-oops-121216113235-phpapp01/85/OOPs-Development-with-Scala-28-320.jpg)
OOPs Development with Scala
- 1. Introduction to Object Oriented Programming Mumbai
- 2. What is an object? Dog Snowy
- 3. Dog is a generalization of Snowy Dog Animal Snowy Subclass?
- 4. Dog Animal Bird Polymorphism?
- 5. object Real world abstractions Encapsulate state represent information state Communicate by Message passing behavior May execute in sequence Or in parallel
- 6. name state behavior
- 7. inheritance encapsulation Building blocks polymorphism
- 8. Inheritance lets you build classes based on other classes, thus avoiding duplicating and repeating code
- 9. When a class inherits from another, Polymorphism allows a subclass to standin for a superclass duck cuckoo Bird.flapWings() ostrich
- 10. Encapsulation is to hide the internal representation of the object from view outside object definition Car.drive() Car drive()
- 11. camry car accord Vehicle toyota motorcycle honda Harley-davidson civic corolla 5 mins
- 13. What the stakeholders want 1 Add flexibility, Remove duplication Encapsulation, 2 Inheritance, Polymorphism 3 Apply patterns Loose coupling Delegation
- 14. We have a product which collects checks from various banks and processes them. The process includes sending out email, a fax or storing a scan for the check.
- 15. Pay attention to the nouns (person, place or thing) they are object candidates The verbs would be the possible methods This is called textual analysis
- 16. We have a product which collects checks from various banks and processes them. The process includes sending out email, a fax or storing a scan for the check. 5 mins
- 17. We have a product which collects checks from various banks and processes them. The process includes sending out email, a fax or storing a scan for the check.
- 18. FastProcessor process(check:Check) Bank sendEmail(check:Check) sendFax(check:Check) scan(check:Check) * Check ---------------- bank:Bank
- 20. case class Bank(id:Int, name:String) case class Check(number:Int, bank:Bank) class FastProcessor { def process(checks:List[Check]) = checks foreach (check => sendEmail) def sendEmail = println("Email sent") } val citibank = new Bank(1, "Citibank") //> citibank : com.baml.ooad.Bank = Bank(1,Citibank) (new FastProcessor).process(List(new Check(1,citibank), new Check(2,citibank))) //> Email sent //| Email sent
- 21. We need to support BoA as well and that sends Faxes
- 22. We dont touch the design
- 23. case class Bank(id:Int, name:String) case class Check(number:Int, bank:Bank) class FastProcessor { def process(checks:List[Check]) = checks foreach (check => if (check.bank.name=="Citibank") sendEmail else sendFax) def sendEmail = println("Email sent") def sendFax = println("Fax sent") } val citibank = new Bank(1, "Citibank") // val bankOfAmerica = new Bank(2, "BoA") // val citibankCheckList = List(new Check(1,citibank), new Check(2,citibank)) val bankOfAmericaCheckList = List(new Check(1,bankOfAmerica), new Check(2,bankOfAmerica)) (new FastProcessor).process(citibankCheckList ::: bankOfAmericaCheckList) //> Email sent //| Email sent //| Fax sent //| Fax sent
- 24. We need to support HDFC and ICICI as well now!
- 25. good design == flexible design whenever there is a change encapsulate it 5 mins
- 26. What the stakeholders want 1 Add flexibility, Remove duplication Encapsulation, 2 Inheritance, Polymorphism 3 Apply patterns Loose coupling Delegation
- 27. trait Bank { def process(check: Check) } object CitiBank extends Bank { val name = "CitiBank" def process(check: Check) = sendEmail def sendEmail = println("Email sent") } object BankOfAmerica extends Bank { val name = "BoA" def process(check: Check) = sendFax def sendFax = println("Fax sent") } object HDFC extends Bank { val name = "HDFC" def process(check: Check) = {sendFax; sendEmail} def sendEmail = println("Email sent") def sendFax = println("Fax sent") } case class Check(number: Int, bank: Bank)
- 28. class FastProcessor { def process(checks: List[Check]) = checks foreach (check => check.bank.process(check)) } val citibankCheckList = List(new Check(1, CitiBank), new Check(2, CitiBank)) val bankOfAmericaCheckList = List(new Check(1, BankOfAmerica), new Check(2, BankOfAmerica)) val hdfcCheckList = List(new Check(1, HDFC)) (new FastProcessor).process(citibankCheckList ::: bankOfAmericaCheckList ::: hdfcCheckList) //> Email sent //| Email sent //| Fax sent //| Fax sent //| Fax sent //| Email sent
- 29. bank FastProcessor HDFC BoA Citibank Check
- 30. bank FastProcessor HDFC BoA Citibank Check
- 31. Code to interfaces – makes software easy to extend Encapsulate what varies – protect classes from changes Each class should have only one reason to change
- 32. What the stakeholders want 1 Add flexibility, Remove duplication Encapsulation, Inheritance, 2 Polymorphism 3 Apply patterns Loose coupling Delegation
- 33. OO Principles result in maintenable, flexible and extensible software
- 34. Open Closed Principle Classes should be open for extension and closed for modification
- 35. bank HDFC BoA Citibank Any number of banks?
- 36. DRY Don't repeat yourself All duplicate code should be encapsulated / abstracted
- 37. bank FastProcessor HDFC BoA Citibank Check CommunicationUtils
- 38. What the stakeholders want 1 Add flexibility, Remove duplication Encapsulation, Inheritance, 2 Polymorphism 3 Apply patterns Loose coupling Delegation
- 39. Single Responsibility Principle Each object should have only one reason to change
- 41. What methods should really belong to Automobile?
- 43. Liskov Substitution Principle Subtypes MUST be substitutable for their base types Ensures well designed inheritance
- 44. Is this valid?
- 45. class Rectangle { var height: Int = 0 var width: Int = 0 def setHeight(h: Int) = { height = h } def setWidth(w: Int) = { width = w } } class Square extends Rectangle { override def setHeight(h: Int) = { height = h; width = h } override def setWidth(w: Int) = { width = w; height = w } } val rectangle = new Square rectangle.setHeight(10) rectangle.setWidth(5) assert(10 == rectangle.height) //> java.lang.AssertionError: assertion failed
- 46. There are multiple options other than inheritance
- 47. Delegation When once class hands off the task of doing something to another Useful when you want to use the functionality of another class without changing its behavior
- 48. bank HDFC BoA Citibank We delegated processing to individual banks
- 49. Composition and Aggregation To assemble behaviors from other classes
- 50. HDFC BoA Citibank CommunicationUtils
- 51. 30 min Exercise Design an OO parking lot. What classes and functions will it have. It should say, full, empty and also be able to find spot for Valet parking. The lot has 3 different types of parking: regular, handicapped and compact.