swift 闭包+嵌套函数+extension+单例+嵌套函数+??

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

import UIKit

//*******************嵌套函数*****************************
func getMathFunc(type:String) -> ((Int) -> Int) {
  func squre(num:Int) -> Int{
     return num * num
  }
  func cube(num:Int) -> Int{
     return num * num * num
  }
  switch (type) {
  case "squre":
    return squre
  default:
    return cube
  }
}

var mathFunc = getMathFunc("squre")
mathFunc(4)
var mathFunc2 = getMathFunc("other")
mathFunc2(4)


//********************闭包****************************
//  {  (形参列表) -> 返回值类型 in
//      可执行表达式
//  }

func getMathFunc1(type:String) -> ((Int) -> Int) {
  func squre(num:Int) -> Int{
    return num * num
  }
  func cube(num:Int) -> Int{
    return num * num * num
  }
  switch (type) {
  case "squre":
    return {(num:Int) -> Int in
        return num * num
     }
  default:
    return {(num:Int) -> Int in
       return num * num * num
    }
  }
}
var maxFunc3 = getMathFunc("squre")
maxFunc3(5)
var maxFunc4 = getMathFunc("other")
maxFunc4(5)

//
var squre: (Int) -> Int = {(num) in return num * num}
squre(3)


//?? 如果??左边有值就就是原值,如果没有值那么就设置为??右边的值
var a:Int?
//a = 11
print(a ?? 2)

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

import UIKit
print("555")

// MARK - guard
func checkup(person:[String:String]){
  guard let id = person["id"] else {
    print("没有id,不能进入")
    return
  }
  guard let exam = person["exam"] else{
    print("没有exam,不能进入")
    return
  }
  print("id:(id),exam:(exam)--批准进入")
}
//checkup(["id":"123"])
//checkup(["exam":"456"])
checkup(["id":"123","exam":"456"])


//MARK - 熟悉观察
let MaxValue = 999
let MinValue = -999
var number = 0 {
   willSet{
   print("从(number)变为(newValue)")
   }
   didSet{
    if number > MaxValue {
       number = MaxValue
    }else if number < MinValue{
      number = MinValue
    }
    print("已经从(oldValue)变为(number)")
   }

}
number = 1000
number


//MARK - 扩展 extension
//对Int扩展,增加一个方法
extension Int {
  func times(closure:(() -> ())?){
    if self >= 0 {
      for _ in 0..<self {
        closure?()
      }
    }
  }
}
3.times{print("走起")}
//MARK 协议扩展
extension CustomStringConvertible{
  var upperDescription:String{
     return self.description.uppercaseString
  }
}
["key":"value"].upperDescription

//map:得到一个由闭包里面的返回值组成的新序列
//flatMap:与map类似的功能,但是会过滤掉返回值里面的nil值
//filter:得到一个由闭包返回值为true的值组成的新序列

var result = [1,2,3,4,5].map{$0 * 2}
result

result = [1,2,3,4,5].filter{$0 > 2}
result

//MARK 单例
class TestObject {
   static let testObject = TestObject()
  //私有构造,保证外部对象通过init方法创建单例类的其他实例
  private init() { }
}

源码下载:https://github.com/pheromone/swift-extension-

            http://download.csdn.net/detail/shaoting19910730/9515986