Swift 3 by example

//: Playground - noun: a place where people can play

import UIKit

// Mutable variable

var str = "Hello, playground"

// Array

var myarr : [String] = ["Watsh", "Rajneesh"]

// Dictionary

var mydict : [String:String] = ["tic": "tac", "ping": "pong"]

// constants

let conststr = "My Const String"

let countup = ["one", "two"]

let mapNameToParkingSpace = ["Alice": 10, "Rajneesh": 12]

// subscript of array

let elem = countup[1]

// Initializers

let emptyString = String()

let emptyArr = [Int]()

let emptySet = Set<Float>()

let defaultNum = Int()

let defaultBool = Bool()

let defaultFloat = Float()

// initializing a set

let availableRoomsSet = Set([1,2,3, 4])

// Properties

emptyArr.count

availableRoomsSet.count

conststr.isEmpty

// Optionals - can be value of the said datatype or nil

var anOptionalFloat: Float?

var anOptionalArrayOfStrings: [String]?

var anOptionalArrayOfOptionalStrings: [String?]?

var reading1: Float?

var reading2: Float?

reading1 = 1.0

reading2 = 2.0

// to use the value we need to unwrap the optional

// 1. forced unwrapping - used when sure that value will not be nil

// if reading2 assignment commented - this will result in error

let avgReading = (reading1! + reading2!)/2

// 2. Optional binding - safe to use always

//  if reading2 assignment is commented out, will go to else block

if let r1 = reading1,

    let r2 = reading2 {

    let avg = (r1 + r2)/2

} else {

    print("reading nil")

}

// Subscripting dictionary

let nameByParkingSpace = [13: "Alice", 27: "Bob"]

let space13Assignee: String? = nameByParkingSpace[13]

let space42Assignee: String? = nameByParkingSpace[42]

if let space13Assignee = nameByParkingSpace[13] {

    print("Key 13 is assigned in the dictionary!")

}

// looping

let range = 0 ..< countup.count

for i in range {

    let string = countup[i]

    // Use 'string'

}

for string in countup {

    // Use 'string'

}

// return a tuple of index and value in array

for (i, string) in countup.enumerated() {

    // (0, "one"), (1, "two")

}

// iterating dictionary

for (space, name) in nameByParkingSpace {

    let permit = "Space \(space): \(name)"

    print(permit)

}

// enum

enum PieType {

    case Apple

    case Cherry

    case Pecan

}

let favoritePie = PieType.Apple

let name: String

// switch-case with enum

// no break required as only the code within the matching case is executed so break is implicit

// fallthrough behavior can be set

switch favoritePie {

case .Apple:

    name = "Apple"

case .Cherry:

    name = "Cherry"

case .Pecan:

    name = "Pecan"

}

let osxVersion: Int = 7

switch osxVersion {

case 0...8:

    print("A big cat")

case 9:

    print("Mavericks")

case 10:

    print("Yosemite")

default:

    print("Greetings, people of the future! What's new in 10.\(osxVersion)?")

}

// Value associated with enum

enum PieTypeInt: Int {

    case Apple = 0

    case Cherry

    case Pecan

}