Swift學習第一天

轉載鏈接：http://www.cocoachina.com/newbie/basic/2014/0604/8675.html

備忘錄：http://www.cocoachina.com/applenews/devnews/2014/0604/8663.html

1. SWift我來了，hello world！

println("hello, world")

備註：這行代碼就是一個完整的程序，不需要導入庫，不需要main函數入口，末尾連分號也不再需要。

2. 使用let來聲明常量，使用var來聲明變量

var myVariable = 42
myVariable = 50
let myConstant = 42

自動檢測類型

let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble: Double = 70

值永遠不會被隱式轉換爲其他類型。如果你需要把一個值轉換成其他類型，請顯式轉換

例如：String() 或 \()

let width = 30
let widthLable = "The width is \(width)"
let widthLabel1 = "The width is" + String(width)
let widthLable2 = "Phone" + " width is \(width)"

3. 使用方括號[]來創建數組和字典，並使用下標或者鍵（key）來訪問元素。

var shoppingList = ["catfish", "water", "tulips", "blue paint"]
shoppingList[1] = "bottle of water"

var occupations = [
    "key1": "value1",
]
occupations["key2"] = "value2"
occupations["key1"] = "value111"

要創建一個空數組或者字典，使用初始化語法

let emptyArray = String[]()
let emptyDictionary = Dictionary<String, Float>()

3. Swith中運行switch中匹配到的子句之後，程序會退出switch語句，並不會繼續向下運行，所以不需要在每個子句結尾寫break

let vegetable = "red pepper"
switch vegetable {
case "celery":
    let vegetableComment = "Add some raisins and make ants on a log."
case "cucumber", "watercress":
    let vegetableComment = "That would make a good tea sandwich."
case let x where x.hasSuffix("pepper"):
    let vegetableComment = "Is it a spicy \(x)?"
default:
    let vegetableComment = "Everything tastes good in soup."
}

let n = 2
switch n {
case 1:
    println("It's 1!")
case 2...4:
    println("It's between 2 and 4!")
case 2..4:
println("It's between 2 and 3!")
case 5, 6:
    println("It's 5 or 6")
default:
    println("Its another number!")
}

備註：...是右閉區間 ..則相反

4. 使用func來聲明一個函數，使用名字和參數來調用函數。使用->來指定函數返回值。

func greet(name: String, day: String) -> String {
    return "Hello \(name), today is \(day)."
}
greet("Bob", "Tuesday")

備註：使用起來像一個閉包