swift 的高阶函数的使用代码

 //: Playground - noun: a place where people can play
 
 import UIKit
 
 var str = "Hello, playground"
 
 /// 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
 var array =  [,,,,]
 var newArray = array.map({$ * })
 print(newArray)
 
  /// 使用reduce 函数 求和
 var sum = array.reduce(, combine: +)
 print(sum)
 
 /// 使用 filter来验证tweet中是否包含选定的若干关键字中的一个
 let words = ["Swift","iOS","cocoa","OSX","tvOS"]
 let tweet = "This is an example tweet larking about Swift"
 let valid = !words.filter({tweet.containsString($)}).isEmpty
 print(valid)
 
 let valid1 = words.contains(tweet.containsString)
 print(valid1)
 
 let valid2 = tweet.characters.split(" ").lazy.map(String.init).contains(Set(words).contains)
 print(valid2)
 
  /// 使用split map 分隔内容
 let text = "窗前明月光 疑是地上霜 举头望明月 低头思故乡"
 let lines = text.characters.split(" ").map(String.init)
 print(lines[])
 print(lines[])
 print(lines[])
 print(lines[])
 
 /// 使用forEach 高阶函数便利
 let name = "urai"
 (...).forEach({print("Happy Birthday " + (($ == ) ? "dear \(name)":"to You"))})
 (...).forEach{print("Happy Birthday " + (($ == ) ? "dear \(name)":"to You"))}
 
 // MARK: - 查找数组中符合条件的数据
 extension SequenceType {
 
     typealias Element = Self.Generator.Element
 
     func partitionBy(fu: (Element) -> Bool) -> ([Element],[Element]) {
 
         var first = [Element]()
         var second = [Element]()
 
         for el in self {
 
             if fu(el) {
 
                 first.append(el)
             }
             else {
 
                 second.append(el)
             }
         }
         return (first,second)
     }
 }
 
 let part = [, , , , , ].partitionBy{$ < }
 print(part)
 
 // MARK: - 一种更简介的查找方式
 extension SequenceType {
 
     func anotherpartitionBy(fu: (Self.Generator.Element) -> Bool) -> ([Self.Generator.Element],[Self.Generator.Element]) {
 
         return (self.filter(fu),self.filter({!fu($)}))
     }
 }
 
 let part1 = [, , , , , ].anotherpartitionBy{$ < }
 print(part1)
 
 /// 使用的是分区元组，但效率不如上边的高
 var part2 = [, , , , , ].reduce( ([],[]), combine: {
     (a:([Int],[Int]),n:Int) -> ([Int],[Int]) in
     (n<) ? (a.+[n],a.) : (a.,a.+[n])
 })
 print(part2)

代码