Swift进阶六——函数和闭包

func play(a: Int) {}

let b = 11play(a: b)

func chooseStepFunc(back: Bool) -> (Int)->Int {    func stepForward(input: Int) -> Int { return input + 1 }    func stepBackward(input: Int) -> Int { return input - 1 }    return back ? stepBackward : stepForward}

func makeIncrementer(forIncrement ammount: Int) -> () -> Int {    var runningTotal = 0    func incrementer() -> Int {        runningTotal += ammount        return runningTotal    }    return incrementer}

let incrementByTen = makeIncrementer(forIncrement: 10)print(incrementByTen()) // 10print(incrementByTen()) // 20print(incrementByTen()) // 30
// 如果你创建了第二个Incrementer，他将会有一个新的、独立的runningTotal的引用。let incrementBySeven = makeIncrementer(forIncrement: 7)print(incrementBySeven()) // 7print(incrementBySeven()) // 14
print(incrementByTen()) // 40

let incrementByTen = makeIncrementer(forIncrement: 10)print(incrementByTen()) // 10print(incrementByTen()) // 20print(incrementByTen()) // 30
let incrementBySeven = makeIncrementer(forIncrement: 7)print(incrementBySeven()) // 7print(incrementBySeven()) // 14
print(incrementByTen()) // 40        // 闭包是引用类型let alsoIncrementByTen = incrementByTenprint(alsoIncrementByTen()) // 50

func someFunctionWithEscapingClosure(closure: @escaping ()->Void) {    closure()}
func someFunctionWithNoneEscapingClosure(closure: ()->Void) {    closure()}
class SomeClass {    var x = 10        func doSomeThing() {        someFunctionWithEscapingClosure {            // 逃逸闭包中必须显示地引用self，否则会报错如下：            // Reference to property 'x' in closure requires explicit 'self.' to make capture semantics explicit            self.x = 100        }                someFunctionWithNoneEscapingClosure {            x = 200        }    }}

public func assert(_ condition: @autoclosure () -> Bool, _ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line)

    var number = 3    assert(number > 3, "number不能大于3")

var names = ["mike", "norman", "lavie"]print(names.count) // 3
// removeOneName是一个闭包表达式，它可以被延迟处理let removeOneName = { names.removeFirst() }print(names.count) // 3
// 此时闭包表达式removeOneName会被执行print("Now remove \(removeOneName())") // Now remove mikeprint(names.count) // 2

func removeName(waitingRemoveName: ()->String) {    print("Now remove \(waitingRemoveName())")}
var names = ["mike", "norman", "lavie"]print(names.count) // 3
removeName(waitingRemoveName: { names.removeFirst() }) // Now remove mikeprint(names.count) // 2

func removeName(waitingRemoveName: @autoclosure()->String) {    print("Now remove \(waitingRemoveName())")}
var names = ["mike", "norman", "lavie"]print(names.count) // 3
removeName(waitingRemoveName: names.removeFirst()) // Now remove mikeprint(names.count) // 2

let NON_WORDS = ["the", "and", "of", "to", "a", "i", "it", "in", "or", "is", "as", "so", "but", "be"]
func wordFreq(words: String) -> [String : Int] {    var wordDic: [String : Int] = [:]    let wordList = words.split(separator: " ")    for word in wordList {        let lowerCaseWord = word.lowercased() // 小写转换        if !NON_WORDS.contains(lowerCaseWord) { // 将不需要统计的筛选出去                        if let count = wordDic[lowerCaseWord] { // 统计出现次数                wordDic[lowerCaseWord] = count + 1            } else {                wordDic[lowerCaseWord] = 1            }        }    }        return wordDic}

let words = """There are moments in life when you miss someone so much that you just want to pick theme from your dreams and hug theme for real dream what you want to dream go where you want to go be what you want to be because you have only one life and one change to do all the things you want to do"""     print(wordFreq(words: words))//["where": 1, "there": 1, "are": 1, "from": 1, "that": 1, "things": 1, "what": 2, "someone": 1, "life": 2, "dreams": 1, "change": 1, "go": 2, "moments": 1, "only": 1, "do": 2, "just": 1, "you": 7, "dream": 2, "hug": 1, "all": 1, "have": 1, "much": 1, "when": 1, "miss": 1, "one": 2, "want": 5, "for": 1, "your": 1, "pick": 1, "real": 1, "because": 1, "theme": 2]

func wordFreq(words: String) -> [String : Int] {    var wordDic: [String : Int] = [:]    let wordList = words.split(separator: " ")        // 函数式解决方案    wordList.map({$0.lowercased()})        .filter({!NON_WORDS.contains($0)})        .forEach { (word) in            wordDic[word] = (wordDic[word] ?? 0) + 1    }        // 面向对象（命令式）解决方案//    for word in wordList {//        let lowerCaseWord = word.lowercased()//        if !NON_WORDS.contains(lowerCaseWord) {//            if let count = wordDic[lowerCaseWord] {//                wordDic[lowerCaseWord] = count + 1//            } else {//                wordDic[lowerCaseWord] = 1//            }//        }//    }        return wordDic}

func cleanNames(names: [String]) -> String {    var cleanNames = ""    for name in names {        if name.count > 1 {            cleanNames += name.capitalized + ","        }    }    cleanNames.remove(at: cleanNames.index(before: cleanNames.endIndex)) // 移除末尾多余的逗号        return cleanNames}

let employee = ["norman", "v", "lavie", "n", "mike", "lily", "zhangsan", "lisi", "wangwu", "w", "jackson", "jams"]print(cleanNames(names: employee)) // Norman,Lavie,Mike,Lily,Zhangsan,Lisi,Wangwu,Jackson,Jams

func cleanNames(names: [String]) -> String {    return names.filter({$0.count > 1})                .map({$0.capitalized})                .joined(separator: ",")}