Swift学习第一天

转载链接：http://www.cocoachina.com/newbie/basic/2014/0604/8675.html

备忘录：http://www.cocoachina.com/applenews/devnews/2014/0604/8663.html

1. SWift我来了，hello world！

 println("hello, world")

备注： 这行代码就是一个完整的程序，不需要导入库，不需要main函数入口，末尾连分号也不再需要。

2. 使用let来声明常量，使用var来声明变量

 var myVariable = 42
 myVariable = 50
 let myConstant = 42

自动检测类型

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

值永远不会被隐式转换为其他类型。如果你需要把一个值转换成其他类型，请显式转换

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. 使用方括号[]来创建数组和字典，并使用下标或者键（key）来访问元素。

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

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

要创建一个空数组或者字典，使用初始化语法

 let emptyArray = String[]()
 let emptyDictionary = Dictionary()

3. Swith中运行switch中匹配到的子句之后，程序会退出switch语句，并不会继续向下运行，所以不需要在每个子句结尾写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!")
 }

备注：...是右闭区间 ..则相反

4. 使用func来声明一个函数，使用名字和参数来调用函数。使用->来指定函数返回值。

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

备注：使用起来像一个闭包