Swift for Complete Beginners

How to install Xcode and create a playground

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

import UIKit

var str = "Hello, playground"

Variables and constants

变量

var name = "Tim McGraw"

var name = "Tim McGraw"
name = "Romeo"

常量

import UIKit
let name = "Tim McGraw"
// name = "Romeo" 不要试图改变常量的值

Types of Data

先声明变量的类型,再赋值:

var name: String
name = "Tim McGraw"

var age: Int
age = 25

有小数部分的默认是 Double

var latitude: Double
latitude = 36.166667

var longitude: Float
longitude = -86.783333
var stayOutTooLate: Bool
stayOutTooLate = true

var missABeat: Bool
missABeat = false

类型推断:

var name = "Tim McGraw"

等价于

var name: String
name = "Tim McGraw"

或者,指定类型并赋值:

var name: String = "Tim McGraw"

Operators

加、减、乘、除、赋值分别对应:+, -, *, /, =

操作及赋值:+=, -=

加一,减一:++, --

比较:>, >=, <

判断:==, !=

取反:!

String interpolation

var name = "Tim McGraw"
var name = "Tim McGraw"
"Your name is \(name)"

Arrays

var oddNumbers = [2, 4, 6, 8]
var songs = ["Shake it Off", "You Belong with Me", "Back to December"]
var songs = ["Shake it Off", "You Belong with Me", "Back to December"]
songs[0]
songs[1]
songs[2]
var songs = ["Shake it Off", "You Belong with Me", "Back to December"]
songs.dynamicType
var songs: [String]
songs[0] = "Shake it Off"
var songs: [String] = []

// 或

var songs = [String]()

数组操作:

var songs = ["Shake it Off", "You Belong with Me", "Love Story"]
var songs2 = ["Today was a Fairytale", "White Horse", "Fifteen"]
var both = songs + songs2

// 或

both += ["Everything has Changed"]

Dictionaries

var person = ["Taylor", "Alison", "Swift", "December", "taylorswift.com"]
var person = ["first": "Taylor", "middle": "Alison", "last": "Swift", "month": "December", "website": "taylorswift.com"]
person["middle"]
person["month"]

Conditional statements

var action: String
var person = "hater"

if person == "hater" {
    action = "hate"
}
var action: String
var person = "hater"

if person == "hater" {
    action = "hate"
} else if person == "player" {
    action = "play"
} else {
    action = "cruise"
}
var action: String
var stayOutTooLate = true
var nothingInBrain = true

if stayOutTooLate && nothingInBrain {
    action = "cruise"
}
if !stayOutTooLate && !nothingInBrain {
    action = "cruise"
}

Loops

for i in 1...10 {
    print("\(i) x 10 is \(i * 10)")
}
var str = "Fakers gonna"

for _ in 1 ... 5 {
    str += " fake"
}

print(str)
var people = ["players", "haters", "heart-breakers", "fakers"]
var actions = ["play", "hate", "break", "fake"]

for i in 0 ... 3 {
    print("\(people[i]) gonna \(actions[i])")
}
var people = ["players", "haters", "heart-breakers", "fakers"]
var actions = ["play", "hate", "break", "fake"]

for i in 0 ..< people.count {
    print("\(people[i]) gonna \(actions[i])")
}
var people = ["players", "haters", "heart-breakers", "fakers"]
var actions = ["play", "hate", "break", "fake"]

for i in 0 ..< people.count {
    var str = "\(people[i]) gonna"

    for _ in 1 ... 5 {
        str += " \(actions[i])"
    }

    print(str)
}

使用 break

var counter = 0

while true {
    print("Counter is now \(counter)")
    ++counter

    if counter == 556 {
        break
    }
}

使用 continue

var songs = ["Shake it Off", "You Belong with Me", "Back to December"]

for song in songs {
    if song == "You Belong with Me" {
        continue
    }

    print("My favorite song is \(song)")
}

Switch case

let liveAlbums = 2

switch liveAlbums {
case 0:
    print("You're just starting out")

case 1:
    print("You just released iTunes Live From SoHo")

case 2:
    print("You just released Speak Now World Tour")

default:
    print("Have you done something new?")
}
let studioAlbums = 5

switch studioAlbums {
case 0...1:
    print("You're just starting out")

case 2...3:
    print("You're a rising star")

case 4...5:
    print("You're world famous!")

default:
    print("Have you done something new?")
}

Functions

定义

func favoriteAlbum() {
    print("My favourite is Fearless")
}

调用

favoriteAlbum()

带参数

func favoriteAlbum(album: String) {
    print("My favourite is \(album)")
}

带返回值

func albumsIsTaylor(name: String) -> Bool {
    if name == "Taylor Swift" { return true }
    if name == "Fearless" { return true }
    if name == "Speak Now" { return true }
    if name == "Red" { return true }
    if name == "1989" { return true }

    return false
}

Optionals

func getHaterStatus() -> String {
    return "Hate"
}
func getHaterStatus() -> String? {
    return "Hate"
}
func getHaterStatus(weather: String) -> String? {
    if weather == "sunny" {
        return nil
    } else {
        return "Hate"
    }
}
var status: String
status = getHaterStatus("rainy")
var status: String?
status = getHaterStatus("rainy")
if let status = getHaterStatus("rainy") {
    takeHaterAction(status)
}

强制转换,将 String? 换为 String!

Optional chaining

func albumReleasedYear(year: Int) -> String? {
    switch year {
    case 2006: return "Taylor Swift"
    case 2008: return "Fearless"
    case 2010: return "Speak Now"
    case 2012: return "Red"
    case 2014: return "1989"
    default: return nil
    }
}

let album = albumReleasedYear(2006)
print("The album is \(album)")
let album = albumReleasedYear(2006)?.uppercaseString
print("The album is \(album)")
let album = albumReleasedYear(2006)?.someOptionalValue?.someOtherOptionalValue?.whatever
let album = albumReleasedYear(2006) ?? "unknown"
print("The album is \(album)")

Enumerations

https://www.hackingwithswift.com/read/0/14/enumerations

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