Code-Formatting-In-Swift

Swift code formatting cheatshet.

Jury is still out - please add an issue for discussion.

General rules

• Indentation by FOUR spaces (␣␣␣␣) instead of TAB (⇥)!
  TAB can be problematic, spaces have always the same width.

• Every block contents always indented.
  Helps with reading/scanning by providing visual hint.

• First argument embedded in method name: openDoors(doors:.
  Adopted from Cocoa/ObjectiveC - can save a bit of space.

• No additional lines if not explicitly stated otherwise.
  The shorter file, the faster reading/scanning.

• One empty line before return if there is more than one line in method.
  Return is very important, should not be ommited by mistake.

Variables and constants

• One space after let / var: let␣computerName.
  One space is enough.

• Space before and after equal sign: computerName␣=␣"HAL9000".
  To improve legibility.

• One space between colon and type: versionNumber:␣Double.
  To improve legibility and differentiate from conformance colon.

Example:

let computerName = "HAL9000"   
let versionNumber: Double = 1

Control operator: IF

• One empty line before every (including first in block) if: ↵if.
  This operator is very important, should be extra visible.

• One empty line after every (excluding last in block) if(else) block: if␣true␣{return}↵↵.
  This operator is very important, should be extra visible.

• Use parenthesis only to improve legibility.
  Only logical monstrosities need that special treatment.

Example:

let someString = "toShowEmptyLine"

if computer.authenticateWithPassword("pass") {
    computer.openDoors("Some doors")
}

println("toShowEmptyLine")

Control operator: SWITCH

• One empty line before every switch: ↵switch.
  This operator is very important, should be extra visible.

• One empty line after every switch block: switch variableName {↵ ... }↵↵.
  This operator is very important, should be extra visible.

• Use parenthesis in case only to improve legibility.
  Only logical monstrosities need that special treatment.

• Indent (␣␣␣␣) every case section as it were block.
  To improve legibility.

Example:

println("flight: ")
var flightNumber = 110

switch flightNumber {
case 0..<110:
    println("is less than 110")
case 110:
    println("is 110")
default:
    println("some other")
}

println("end")

Protocol declaration

• One space between method parameter name+colon and type: doors:␣String.
  To improve legibility and differentiate from conformance colon.

• One space before and after return type arrow )␣->␣String.
  To improve legibility.

• One space before opening bracket ␣{.
  To improve legibility.

Example:

protocol DoorOperator {
	func openDoors(doors: String) -> String
}

Class declaration

• One space before and one after conformance colon: HAL9000␣:␣DoorOperator.
  To improve legibility and differentiate from other colon applications.

• One space before opening bracket ␣{.
  To improve legibility.

• One blank line separation from properties declaration and methods.
  To provide visual separation.

• One blank line between methods declarations.
  To provide visual separation.

• Computed properties declarations shall be treated as methods.
  They act like methods. Should be treated as just a special case.

Example:

class HAL9000 : DoorOperator {
    let debugDescription = "HAL9000"
    let softwareVersion = 2.1

    func openDoors(doors: String) -> String {
        return ("\(debugDescription) v\(softwareVersion): Affirmative. Opened \(doors).")
    }
}

class CurrentComputer : DoorOperator {
    private var computer: HAL9000!

    var debugDescription: String {
        get {
            let computerDescription = self.computer?.debugDescription
                                                   ?? "(no computer)"

            return "computer: \(computerDescription)"
        }
    }

    func authenticateWithPassword(pass: String) -> Bool {

        if pass != "pass" {
            return false
        }
        
        computer = HAL9000()

        return true
    }

    func openDoors(doors: String) -> String {

        if computer == nil {
            return "Access Denied. I'm afraid I can't do that."
        }
        
        return computer.openDoors(doors)
    }
}