#Swift Cheat Sheet

A quick cheat sheet and reference guide for Apple's Swift language. Guide covers all the key features of Swift, including Strings, Arrays, Dictionaries and Flow Control. There are few others on github, but this one is trying to keep it simple.

###Variables

var myInt = 1
var myExplicitInt: Int = 1 // explicit type
var x = 1, y = 2, z = 3 // declare multiple integers
myExplicitInt = 2 // set to another integer value

###Constants

let myInt = 1
myInt = 2 // compile-time error!

###Strings

var myString = "a"
let myImmutableString = "c"
myString += "b" // ab
myString = myString + myImmutableString // abc
myImmutableString += "d" // compile-time error!

let count = 7
let message = "There are \(count) days in a week"

###Logical Operators

var happy = true
var sad = !happy // logical NOT, sad = false
var everyoneHappy = happy && sad // logical AND, everyoneHappy = false
var someoneHappy = happy || sad // logical OR, someoneHappy = true

###Printing

let name = "swift"
println("Hello")
println("My name is \(name)")
print("See you ")
print("later")
/*  Hello
    My name is swift
    See you later */

###Arrays

var colors = ["red", "blue"]
var moreColors: String[] = ["orange", "purple"] // explicit type
colors.append("green") // [red, blue, green]
colors += "yellow" // [red, blue, green, yellow]
colors += moreColors // [red, blue, green, yellow, orange, purple]

var days = ["mon", "thu"]
var firstDay = days[0] // mon
days.insert("tue", atIndex: 1) // [mon, tue, thu]
days[2] = "wed" // [mon, tue, wed]
days.removeAtIndex(0) // [tue, wed]

###Dictionaries

var days = ["mon": "monday", "tue": "tuseday"]
days["tue"] = "tuesday" // change the value for key "tue"
days["wed"] = "wednesday" // add a new key/value pair

var moreDays: Dictionary = ["thu": "thursday", "fri": "friday"]
moreDays["thu"] = nil // remove thu from the dictionary
moreDays.removeValueForKey("fri") // remove fri from the dictionary

##Conditionals ###If Statement

let happy = true
if happy {
    println("We're Happy!")
} else {
    println("We're Sad :('")
}

// We're Happy!

let speed = 28
if speed <= 0 {
    println("Stationary")
} else if speed <= 30 {
    println("Safe speed")
} else {
    println("Too fast!")
}

// Safe speed

###Switch

let n = 2
switch n {
case 1:
    println("It's 1!")
case 2...4:
    println("It's between 2 and 4!")
case 5, 6:
    println("It's 5 or 6")
default:
    println("Its another number!")
}

// It's between 2 and 4!

###For Loops

for var index = 1; index < 3; ++index {
	// loops with index taking values 1,2 
}
for index in 1..3 {
	// loops with index taking values 1,2
}
for index in 1...3 { 
	// loops with index taking values 1,2,3
}

let colors = ["red", "blue", "yellow"]
for color in colors {
    println("Color: \(color)")
}

// Color: red
// Color: blue
// Color: yellow 

let days = ["mon": "monday", "tue": "tuesday"]
for (shortDay, longDay) in days {
    println("\(shortDay) is short for \(longDay)")
}
// mon is short for monday
// tue is short for tuesday

###While Loops

var count = 1
while count < 3 {
    println("count is \(count)")
    ++count
}

// count is 1
// count is 2

count = 1
while count < 1 {
    println("count is \(count)")
    ++count
}

//

count = 1
do {
    println("count is \(count)")
    ++count
} while count < 3

// count is 1
// count is 2

count = 1
do {
    println("count is \(count)")
    ++count
} while count < 1

// count is 1

###Functions

func iAdd(a: Int, b: Int) -> Int {
  return a + b
}
iAdd(2, 3) // returns 5

func eitherSide(n: Int) -> (nMinusOne: Int, nPlusOne: Int) {
  return (n-1, n+1)
}
eitherSide(5) // returns the tuple (4,6)

###Classes

class TipCalculator {

  // Properties
  let total: Double
  let taxPct: Double
  let subtotal: Double

  init(total:Double, taxPct:Double) {
    self.total = total // init parameters have same name as properties, so we need to use self.
    self.taxPct = taxPct
    subtotal = total / (taxPct + 1)
  }

  // Method example with return
  func calcTipWithTipPct(tipPct:Double) -> Double {
    return subtotal * tipPct
  }

  func printPossibleTips() {
    //Array example 
    let possibleTipsInferred = [0.15, 0.18, 0.20]
    let possibleTipsExplicit:[Double] = [0.15, 0.18, 0.20]

    for possibleTip in possibleTipsInferred {
      println("\(possibleTip*100)%: \(calcTipWithTipPct(possibleTip))")
    }
  }

}

// Create instance of Class
let tipCalc = TipCalculator(total: 33.25, taxPct: 0.06)
// Method Call
tipCalc.printPossibleTips()