Scala Notes

Other notes

• http://docs.scala-lang.org/cheatsheets/
• t._2 // Part of a method name, such as tuple getters http://stackoverflow.com/a/8001132

Scala for the Impatient

Chapter 1 - Basics

• val immutable, constants. should use val in most cases
• var mutable
• types of values and variables are inferred from the expression that they are initialized with, but you can specify type
  • e.g. val greeting: String = null or val greeting: String = "Hi"
• everything is an object including numbers (e.g. 3.toString()
• Scala compile converts primitives (1, "hi") to wrappers
• Scala has its own classes like RichInt, RichChar, StringOps, etc that wrap Int, Char, String, etc to provide greater functionality
• {}.isInstanceOf[Unit] is True
• operators + - * / % are methods
  • e.g. a + b is equivalent to a.+(b)
• method calls can be written in two ways: a method b or a.method(b)
• a tuple is similar to an Array however it can contain items of differing types
• tuple indexes start at 1, not 0 as in an Array
• toMap takes a collection and turns it into a Map
• “static” function calls don’t look like Java’s static function calls that are called from classes
  • e.g. (scala) pow(2,4)
• there are no static function, instead singleton obkects
• methods without params are called without parentheses

Chapter 2

Chapter 5 - classes

• provides getter and setter methods for every field by default (so you don’t have to go crazy like one may do in Java, creating getters and setters for everything)
  • getters are named after the field, and setters are named after the field with a _ appended to the end. e.g. age and age_
  • Scala will create a class for the JVM from the one below with a private age field, and public getter and setter methods (you can make them private if you declare age private)

      class Person {
        var age = 0
      }
    

• you can also create a field using val but it’ll only have a getter (because it’s immutable!!), not setter