Scala Classes

Question 1

Case Class

Answer 1

Plain and Immutable class that is exclusively supposed to be defined by its constructor arguments.

Should be algebraic datatypes - should not be doing complex calculations inside the class.

Can be pattern-matched

If it extends another class, it must declare the parent class’s parameters or else it’s companion object will not be able to use them (thus the methods in companion obj will act like the parameters inherited from the parent are not there)

Question 2

Trait

Answer 2

Can be used to add methods onto different classes

Question 3

abstract class

Answer 3

A class that is designed to be extended, but not instantiated itself.

  abstract class Car {
             val year: Int
             val automatic: Boolean = true
             def color: String 
  }

Question 4

anonymous class

Answer 4

A class that is made to to be used just once, using the abstract syntax without any parameters

abstract class Listener { def trigger }

Question 5

self type

Answer 5

A type used on a trait to declare that it is only to be used with a certain class.

class A { def hi = “hi” }

  trait B { self: A =>
    def woo = "B" + hi
  }

class C extends B // ERROR: ILLEGAL INHERITANCE

  class C extends A with B
  val obj = new C()
  obj.woo == "Bhi" // true