Writing good readable code in Scala. Guide followed at www.knoldus.com

1. Scala Style Guide
27 Jul 2012 > Vikas Hazrati > vikas@knoldus.com > @vhazrati

2. Indentation
2 spaces Line wrapping

3. Indentation
Methods with several arguments

4. Naming convention
Camel case
Class KnoldusKnowledgeSession
Object – same like class
Methods, Variables, values, Annotations
def myFairMethod = ...

5. Parentheses for methods
foo1 can be accessed with or without parentheses
foo2 cannot be accessed with parentheses
Accessors do not define parentheses
Call site should follow the declaration convention
No parentheses, when the method has no side effect

6. Symbolic method names
! :: => Avoid
Symbolic method names should be reserved for
1. DSL
2. Logically mathematical operations (e.g. a + b
or c :: d)
3. Purely functional operations like joining
Monads (>>=)

7. Type Parameters
Single
More than one

8. Brevity
def add(a: Int, b: Int) = a + b Bad in java
Good in scala
Readable
Few local fields involved
Concise code

9. Void Methods

10. Functions
Space between argument and return type

11. Nested Blocks
def foo = {
Should define brace on line of declaration
}
Splitting parentheses have a space

12. Classes
Single line
Four spaces
Two spaces

13. Ordering in a class
New line between
declarations
Fields before use in
methods
def foo(bar: Baz): Bin = expr
def foo(bar: Baz) { // return type is Unit
expr
}

14. Functional Values
val f1 = { (a: Int, b: Int) => a + b }
val f2 = (a: Int, b: Int) => a + b
val f3 = (_: Int) + (_: Int)
val f4: (Int, Int) => Int = { _ + _ }

15. Control Structures

16. Comprehensions

17. Trivial Conditions
val res = if (foo) bar else baz

18. Files
Single logical compilation unit
Inbox.scala

19. Multiple files
Cohesive group
All multi-unit files should be given camelCase names
with a lower-case first letter.
Help in identification

20. ScalaDoc
It is important to provide documentation for all
packages, classes, traits, methods, and other
members.

21. ScalaDoc

22. Avoid!
Method Returns → returns <what>
This class does XXX - > Does <what>
Links to Scala lib classes as [[scala.option]]
@return
Document what method 'does not' and 'should not' do
first sentence should be a summary of what the method does.
Subsequent sentences explain in further detail

23. Packages
Overview of main
classes
Examples of how to
Use class

24. Classes, Objects & Traits