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()
 var mathFunc2 = getMathFunc("other")
 mathFunc2()

 //********************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()
 var maxFunc4 = getMathFunc("other")
 maxFunc4()

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

 //?? 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 ?? )

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

import UIKit
print("")

// 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":"","exam":""])

//MARK - 熟悉观察
let MaxValue =
let MinValue = -
var number =  {
   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 =
number

//MARK - 扩展 extension
//对Int扩展,增加一个方法
extension Int {
  func times(closure:(() -> ())?){
    if self >=  {
      for _ in ..<self {
        closure?()
      }
    }
  }
}
.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 = [,,,,].map{$ * }
result

result = [,,,,].filter{$ > }
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