ios Swift 备忘录

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 STATEMENT

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 Counter {

  var count: Int = 0

  func inc() {

    count++

  }

  func add(n: Int) {

    count += n

  }

  func printCount() {

    println("Count: \(count)")

  }

}

var myCount = Counter()

myCount.inc()

myCount.add(2)

myCount.printCount() // Count: 3