Swift Section Four(函数与闭包)

函数与闭包

---

//: Playground - noun: a place where people can play

import UIKit

//swift 第四课 函数与闭包

//1.函数的用法
func greet(name: String, day: String) ->String {

return "Hello \(name), today is \(day)"

}

greet("Bob","Tuesday")


//2.多返回值的函数
func calculateStatistics(scores: [Int]) ->(min: Int, max: Int, sum: Int){

var min = scores[0]

var max = scores[0]

var sum = 0

for score in scores{

if score > max {

max = score

}else if score < min{

min = score

}

sum += score

}

return (min, max, sum)

}

let statistics = calculateStatistics([5, 3, 100, 3, 9])

print(statistics.sum)

print(statistics.2)

//3.不限参数个数的函数
func sumOf(numbers: Int...) -> Int {

var sum = 0

for number in numbers{

sum += number

}

return sum

}

sumOf()

sumOf(42, 597, 12)

//4.嵌套函数
func returnFifteen() -> Int{

var y = 10

func add(){

y += 5

}

add()

return y

}

returnFifteen()

//5.函数可以作为函数的返回值
func makeIncrementer() -> (Int -> Int){

func addOne(number: Int) -> Int {

return 1 + number

}

return addOne

}

var increment = makeIncrementer()

increment(7)

//5.函数也可以作为函数的参数
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, 5, 12]

hasAnyMatches(numbers, lessThanTen)


//6.闭包的使用
//首先介绍一下map方法的定义：返回一个数组，这个数组内的元素是原数组经过闭包函数计算返回的值

numbers.map({

(number: Int) -> Int in

let result = 3 * number

return result

})

//简写方式
let mappedNumbers = numbers.map({

number in 3 * number

})

print(mappedNumbers)

//利用闭包排序
let sortedNumbers = numbers.sorted {

$0 > $1

}

print(sortedNumbers)

源代码请前往我的github