课程来自慕课网liuyubobobo老师
函数
- 函数基础
func sayHello(name: String?) -> String {
return "Hello " + ( name ?? "Guest" )
}
var nickname: String? = nil
sayHello(name: nickname)
- 使用元组返回多个值
func findMaxAndMin( numbers: [Int] ) -> ( max: Int, min: Int )? {
if numbers.isEmpty {
return nil
}
var minValue = numbers[0]
var maxValue = numbers[0]
for number in numbers {
minValue = minValue < number ? minValue : number
maxValue = maxValue > number ? maxValue : number
}
return (maxValue, minValue)
}
var scores: [Int]? = [21,123,53,122,33,252]
scores = scores ?? nil
if let result = findMaxAndMin(numbers: scores!) {
print(result.max)
print(result.min)
}
- 函数的命名
func sayHello(to name: String, with greeting: String) -> String {
return "\(greeting),\(name)"
}
sayHello(to: "imooc", with: "Hello")
func mutiple(_ num1: Int,_ num2: Int) -> Int {
return num1 * num2
}
mutiple(4, 2)
- 默认参数值
func sayHello(to name: String = "Playground", with greeting: String = "Hello") -> String {
return "\(greeting),\(name)"
}
sayHello(to: "imooc", with: "Hi") // Hi,imooc
sayHello(to: "bobobo") // Hello,bobobo
sayHello()// Hello,Playground
- 可变参数
func mean(_ numbers:Double ...) -> Double {
var sum:Double = 0
// 将变长参数当做一个数组看待
for number in numbers {
sum += number
}
return sum/Double(numbers.count)
}
mean(2) // 2
mean(2,3) // 2.5
mean(2,3,41,5,1,23,4,52) // 16.375
func sayHello(to names: String ... , with greeting: String = "Hello") {
for name in names {
print("\(greeting),\(name)")
}
}
sayHello(to: "A","B","C", with: "Hi")
- 常量参数、变量参数和inout参数 -> Swift3
// 变量参数不再使用
// inout关键字写在参数后面
// 交换两个整型
func swapTwoInts(_ a: inout Int , _ b : inout Int) {
(a,b) = (b,a)
}
var numA: Int = 3
var numB: Int = 4
swapTwoInts(&numA, &numB)
numA // 4
numB // 3
// 将一个整型数组每一个元素都初始化成0
func initArray(arr: inout [Int], by value:Int ) {
for i in 0..<arr.count {
arr[i] = value
}
}
var arr = [1,2,3]
initArray(arr: &arr, by: 0)
arr // [0,0,0]
- 函数类型
// 产生一个随机数组
var arr: [Int] = []
for _ in 0..<100 {
arr.append(Int(arc4random()%1000))
}
// 按从大到小排序
func biggerNumberFirst (a: Int , b: Int) -> Bool {
return a > b
}
arr.sort(by: biggerNumberFirst)
// 按最接近500排序
func near500 (a: Int, b: Int) -> Bool {
return abs(a-500) < abs(b-500) ? true : false
}
arr.sort(by: near500)
- 函数式编程初步
func changeScores ( scores: inout [Int], by changeScore:(Int) -> Int ) {
for (index,score) in scores.enumerated() {
scores[index] = changeScore(score)
}
}
func changeScore1 (score: Int) -> Int {
return Int(sqrt(Double(score))*10)
}
func changeScore2 (score: Int) -> Int {
return Int(Double(score)/150.0*100.0)
}
var scores1 = [67,72,45,96,80]
changeScores(scores: &scores1, by: changeScore1)
var scores2 = [123,78,96,102,88]
changeScores(scores: &scores2, by: changeScore2)
//map
var scores = [67,72,45,96,80]
scores.map(changeScore1) // [81, 84, 67, 97, 89]
scores // [67,72,45,96,80]
//filter
func fail(score: Int) -> Bool {
return score < 60
}
scores.filter(fail) // [45]
scores // [67,72,45,96,80]
//reduce
func add(num1: Int, num2: Int ) -> Int {
return num1 + num2
}
scores.reduce(0, add) // 360
scores.reduce(0, +) // 360
- 返回函数类型和函数嵌套
// 两种邮费计算方法
func tier1MailFee(by weight: Int) -> Int {
return 1 * weight
}
func tier2MailFee(by weight: Int) -> Int {
return 3 * weight
}
// 计算商品总花费（邮费+商品价格）
func fee(price: Int, weight: Int) -> Int {
// 嵌套选择邮费计算方法的函数
func chooseMailFeeCalculation(by weight: Int) -> (Int) -> Int {
return weight <= 10 ? tier1MailFee : tier2MailFee
}
let mailFeeByWeight = chooseMailFeeCalculation(by: weight)
return mailFeeByWeight(weight) + price
}
fee(price: 100, weight: 10) // 110
fee(price: 100, weight: 20) // 160
