swift 的高阶函数的使用代码
1 //: Playground - noun: a place where people can play 2 3 import UIKit 4 5 var str = "Hello, playground" 6 7 /// 使用map函数，进行数组内部数据的转换，map中接受一个转换函数 8 var array = [1,2,3,4,5] 9 var newArray = array.map({$0 * 2}) 10 print(newArray) 11 12 13 /// 使用reduce 函数 求和 14 var sum = array.reduce(0, combine: +) 15 print(sum) 16 17 18 /// 使用 filter来验证tweet中是否包含选定的若干关键字中的一个 19 let words = ["Swift","iOS","cocoa","OSX","tvOS"] 20 let tweet = "This is an example tweet larking about Swift" 21 let valid = !words.filter({tweet.containsString($0)}).isEmpty 22 print(valid) 23 24 let valid1 = words.contains(tweet.containsString) 25 print(valid1) 26 27 let valid2 = tweet.characters.split(" ").lazy.map(String.init).contains(Set(words).contains) 28 print(valid2) 29 30 31 /// 使用split map 分隔内容 32 let text = "窗前明月光 疑是地上霜 举头望明月 低头思故乡" 33 let lines = text.characters.split(" ").map(String.init) 34 print(lines[0]) 35 print(lines[1]) 36 print(lines[2]) 37 print(lines[3]) 38 39 40 /// 使用forEach 高阶函数便利 41 let name = "urai" 42 (1...4).forEach({print("Happy Birthday " + (($0 == 3) ? "dear \(name)":"to You"))}) 43 (1...4).forEach{print("Happy Birthday " + (($0 == 3) ? "dear \(name)":"to You"))} 44 45 46 // MARK: - 查找数组中符合条件的数据 47 extension SequenceType { 48 49 typealias Element = Self.Generator.Element 50 51 func partitionBy(fu: (Element) -> Bool) -> ([Element],[Element]) { 52 53 var first = [Element]() 54 var second = [Element]() 55 56 for el in self { 57 58 if fu(el) { 59 60 first.append(el) 61 } 62 else { 63 64 second.append(el) 65 } 66 } 67 return (first,second) 68 } 69 } 70 71 let part = [82, 58, 76, 49, 88, 90].partitionBy{$0 < 60} 72 print(part) 73 74 // MARK: - 一种更简介的查找方式 75 extension SequenceType { 76 77 func anotherpartitionBy(fu: (Self.Generator.Element) -> Bool) -> ([Self.Generator.Element],[Self.Generator.Element]) { 78 79 return (self.filter(fu),self.filter({!fu($0)})) 80 } 81 } 82 83 let part1 = [82, 58, 76, 49, 88, 90].anotherpartitionBy{$0 < 60} 84 print(part1) 85 86 /// 使用的是分区元组，但效率不如上边的高 87 var part2 = [82, 58, 76, 49, 88, 90].reduce( ([],[]), combine: { 88 (a:([Int],[Int]),n:Int) -> ([Int],[Int]) in 89 (n<60) ? (a.0+[n],a.1) : (a.0,a.1+[n]) 90 }) 91 print(part2)
代码
