Chapter 58

- 1. Number of legs
  2. Colour of paws
  3. Colour of eyes
  4. Age
  5. Name
- 1. Shortest side length
  2. Longest side length
- 1. Start date
  2. End date
  3. Accomodation price per night
  4. Owner

 // how dare you use 3-space indentation
 class Radio
     // instance variables
     private volume
     private station
     private switch

     public procedure new(aVolume, aStation, aSwitch)
         volume = aVolume
         station = aStation
         switch = aSwitch
     endprocedure

     public procedure setVolume(aVolume)
         volume = aVolume
     endprocedure
 endclass

 robertsRadio = new Radio(0.3, 88.2, false)
 philipsRadio = new Radio(0.6, 37.4, true)

squeak

 class Rodent inherits Animal
     private colour
     public procedure new(aName, aPosition, aSize)
         super.new(aName, aPosition)
         // shame on the book for getting this wrong!
         size = aSize
     endprocedure
 endclass

tom.position increases by 3 and jerry.position increases by 2

Exercises

- 1. Member
    1. JuniorMember
    2. SeniorMember
- ```
  class Member
      private memberNumber
      private firstname
      private surname
      private tel

      public procedure new(aMemberNumber, aFirstname, aSurname, aTel)
          memberNumber = aMemberNumber
          firstname = aFirstname
          surname = aSurname
          tel = aTel
      endprocedure
  endclass
```
- Encapsulation is the independence of an object's methods and attributes from all other objects of its class.
- - Instantiation of an object is where the object is created, with a set of attribute values unique that instance. Only a specific instance of a class can read/write to the attributes of that instance
  - member = new Member("A456", "John", "Bell", "07981 345987")
- 1. Crawlers
    1. Spiders
    2. Bugs
- - type
  - spin_web
- The practice of having a programming language interpret an object differently depending on its class, via subclassing and method overriding
- - Assuming the procedure call is implied:
    
    Birds can fly Seabirds can fly and swim
    
    Otherwise, nothing.
  - bird1 is an instance of Bird. Therefore it uses Bird's move procedure - and prints Birds can fly.
    
    bird2 is an instance of Seabird. Seabird inherits move from Bird, but then overrides it with its own move method, which prints Seabirds can fly and swim.