Ternary Conditional Operator, Nil-Coalescing Operator

Swift Programming Language Guide: Basic Operators. 코드부분

/* Ternary Conditional Operator */

// The ternary conditonal operator is a special operator with three parts, which takses the form question ? answer 1 : answer2.

if question {

    answer1

} else {

    answer2

}

let contentHeight = 40

let hasHeader = true

let rowHeight = contentHeight + (hasHeader ? 50 : 20)

let contentHeigth = 40

let hasHeader = true

let rowHeight: Int

if hasHeader {

    rowHeight = contentHeigth + 50

} else {

    rowHeight = contentHeigth + 20

}

/* Nil-Coalescing Operator */

//The nil-coalescing operator (a ?? b) unwraps an optional a if it contains a value, or returns a default value b if a is nil.

a != nil ? a! : b

let defaultColorName = "red"

var userDefinedColorName: String?

var colorNameToUse = userDefinedColorName ?? defaultColorName

userDefinedColorName = "green"

colorNameToUse = userDefinedColorName ?? defaultColorName

App, MyMemory

Sample Application for Practice 

MyMemory

(참고: 꼼꼼한 재은씨의 스위프트 실전편, 이재은, 루비페이퍼) 

App, ToDoList

Sample Application for Practice 

ToDoList 

(참고: 야곰의 iOS 프로그래밍, Inflearn) 

Subscripts

Swift Programming Language Guide: Subscripts 코드 부분

/* Subscripts */

// Subscript Syntax

subscript(index: Int) -> Int {

   get {

   }

   set(newValue) {

   }

}

struct TimesTable {

   let multiplier: Int

   subscript(index: Int) -> Int {

       return multiplier * index

   }

}

let threeTimesTable = TimesTable(multiplier: 3)

print("six times three is \(threeTimesTable[6])")

// Subscript Usage

var numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]

numberOfLegs["bird"] = 2

// Subscript Options

struct Matrix {

   let rows: Int, columns: Int

   var grid: [Double]

   init(rows: Int, columns: Int) {

       self.rows = rows

       self.columns = columns

       grid = Array(repeating: 0.0, count: rows * columns)

   }

   func indexIsValid(row: Int, column: Int) -> Bool {

       return row >= 0 && row < rows && column >= 0 && column < columns

   }

   

   subscript(row: Int, column: Int) -> Double {

       get {

           assert(indexIsValid(row: row, column: column), "Index ouf of range")

           return grid[(row * columns) + column]

       }

       set {

           assert(indexIsValid(row: row, column: column), "Index out of range")

           grid[(row * columns) + column] = newValue

       }

   }

}

var matrix = Matrix(rows: 2, columns: 2)

matrix[0, 1] = 1.5

matrix[1, 0] = 3.2