ay")
上面是函数的定义，以func关键字定义，括号内是参数的标签、名称和类型内容，返回值通过->指定。
上面函数需要输入参数名称，如果不需要参数名称，可以通过下划线省略输入，如下
func greet(_ person: String, on day: String) -> String {
return "Hello \(person), today is \(day)."
}
greet("John", on: "Wednesday")
另外参数名称可以使用标签名称。
func greet(person: String, from hometown: String) -> String {
return "Hello \(person)! Glad you could visit from \(hometown)."
}
print(greet(person: "Bill", from: "Cupertino"))
// Prints "Hello Bill! Glad you could visit from Cupertino."
嵌套函数如下所示。
func returnFifteen() -> Int {
var y = 10
func add() {
y += 5
}
add()
return y
}
returnFifteen()
复杂一点的函数的参数可以传入函数进行使用，这种类似闭包的处理了
func hasAnyMatches(list: [Int], condition: (Int) -> Bool) -> Bool {
for item in list {
if condition(item) {
return true
}
}
return false
}
func lessThanTen(number: Int) -> Bool {
return number < 10
}
var numbers = [20, 19, 7, 12]
hasAnyMatches(list: numbers, condition: lessThanTen)
下面是一个闭包的函数，闭包通过in 来区分参数和返回的函数体
numbers.map({ (number: Int) -> Int in
let result = 3 * number
return result
})
class Shape {
var numberOfSides = 0
func simpleDescription() -> String {
return "A shape with \(numberOfSides) sides."
}
}
类的定义通过class关键字进行标识，默认的权限是internal，在项目模块内部可以访问的，非常方便。
使用则如下所示，可以通过点语法直接获取属性和调用方法。
var shape = Shape()
shape.numberOfSides = 7
var shapeDescription = shape.simpleDescription()
class NamedShape {
var numberOfSides: Int = 0
var name: String
init(name: String) {
self.name = name
}
func simpleDescription() -> String {
return "A shape with \(numberOfSides) sides."
}
}
类通过使用init的指定名称作为构造函数，使用deinit来做析构函数，使用self来获取当前的类引用，类似于其他语言的this语法，super获取基类的引用。
其他的处理方式如继承、重写的语法和C#类似。
class Square: NamedShape {
var sideLength: Double
init(sideLength: Double, name: String) {
self.sideLength = sideLength
super.init(name: name)
numberOfSides = 4
}
func area() -> Double {
return sideLength * sideLength
}
override func simpleDescription() -> String {
return "A square with sides of length \(sideLength)."
}
}
let test = Square(sideLength: 5.2, name: "my test square")
test.area()
test.simpleDescription()
类的属性使用get、set语法关键字，和C#类似
class EquilateralTriangle: NamedShape {
var sideLength: Double = 0.0
init(sideLength: Double, name: String) {
self.sideLength = sideLength
super.init(name: name)
numberOfSides = 3
}
var perimeter: Double {
get {
return 3.0 * sideLength
}
set {
sideLength = newValue / 3.0
}
}
class TriangleAndSquare {
var triangle: EquilateralTriangle {
willSet {
square.sideLength = newValue.sideLength
}
}
var square: Square {
willSet {
triangle.sideLength = newValue.sideLength
}
}
类属性的赋值可以进行观察，如通过willSet在设置之前调用，didSet在设置之后调用，实现对属性值得监控处理。
enum Rank: Int {
case ace = 1
case two, three, four, five, six, seven, eight, nine, ten
case jack, queen, king
func simpleDescription() -> String {
switch self {
case .ace:
return "ace"
case .jack:
return "jack"
case .queen:
return "queen"
case .king:
return "king"
default:
return String(self.rawValue)
}
}