code-standards.md

The Official XX Network Kotlin Style Guide (in progress)

Goals

Use of this style guide ensures:

• Maintainability
• Conciseness
• Readability
• Simplicity

Inspiration

Most of this guide statements are drawn or adapted from one of the following sources:

Google Java Style Guide - Old school can still be contemporary

Android Kotlin Style Guide - Official Android style guide

Kotlin Coding Conventions - Official Kotlin guidelines for coding

Android Contributors Style Guide - Contribution insights on open sourcing

Google Swift Guide - General Formatting and Rules that can be applied to Kotlin, as they share many syntax similarities

Table of Contents

Click to expand

• Naming
  • Packages
  • Classes, Objects & Interfaces
  • Methods
  • Properties
  • Variables
  • Other
• Resources Naming
  • General Rule
  • Main Types
  • Icons
  • Selector States
  • Strings
  • Dimensions
  • Layouts
• Formatting
  • Indentation
  • Line Wrapping
  • Line Break
  • Break At Operators
  • Assignment Operator
  • Method Calls in Chain
  • Long Parameters Case
  • Vertical Indentation
  • Horizontal Indentation
  • Horizontal Operators Indentation
• Modifiers
  • Public Modifier
  • Other Visibility Modifiers
• Classes, Variables & Objects
  • Variable Declaration
  • Classes
  • Data Classes
  • Enum Classes
  • Getters & Setters
  • Companion Objects
• Conditionals & Braces
  • Braces
  • If Statements
  • When Statements
• Types
  • Immutable Types
  • Nullable Types
  • Type Inference
• Misc
  • Comments
  • Language

Naming

Kotlin is a JVM-compatible language like Java, and naming should follow Kotlin standards.

Packages

• Package names are all lower-case
• Multiple words are discouraged
• If multiple words are needed, they can be used concatenated together, without hyphens or underscores

BAD ⛔:

io.Elixxir.some_widget

GOOD ✅:

io.elixxir.somewidget

Classes, Objects & Interfaces

• Written in UpperCamelCase

BAD ⛔:

open class myExampleClass { /*...*/ }
object emptyObject : myExampleClass() { /*...*/ }
interface myInterface { /*...*/}

GOOD ✅:

open class MyExampleClass { /*...*/ }
object EmptyExampleClass : MyExampleClass() { /*...*/ }
interface MyInterface { /*...*/}

Methods

• Written in lowerCamelCase, without hyphens or underscores

BAD ⛔:

fun ProcessRequests() { /*...*/ }
var finishedCount = 1

GOOD ✅:

fun processRequests() { /*...*/ }
var finishedCount = 1

Properties

• Generally, written in lowerCamelCase
• Properties should not be named with Hungarian notation, as it is as it is not recommended by Google
• Constant values in the companion object should be written all uppercase using underscores in cases with multiple words

Example property names

BAD ⛔:

class MyClass {
  var publicfield: Int = 0
  val Person = Person()
  private var mPrivateField: Int?
}

GOOD ✅:

class MyClass {
  var publicField: Int = 0
  val person = Person()
  private var privateField: Int?
}