swift 闭包+嵌套函数+extension+单例+嵌套函数+??

 1 //: Playground - noun: a place where people can play
 2 
 3 import UIKit
 4 
 5 //*******************嵌套函数*****************************
 6 func getMathFunc(type:String) -> ((Int) -> Int) {
 7   func squre(num:Int) -> Int{
 8      return num * num
 9   }
10   func cube(num:Int) -> Int{
11      return num * num * num
12   }
13   switch (type) {
14   case "squre":
15     return squre
16   default:
17     return cube
18   }
19 }
20 
21 var mathFunc = getMathFunc("squre")
22 mathFunc(4)
23 var mathFunc2 = getMathFunc("other")
24 mathFunc2(4)
25 
26 
27 //********************闭包****************************
28 //  {  (形参列表) -> 返回值类型 in
29 //      可执行表达式
30 //  }
31 
32 func getMathFunc1(type:String) -> ((Int) -> Int) {
33   func squre(num:Int) -> Int{
34     return num * num
35   }
36   func cube(num:Int) -> Int{
37     return num * num * num
38   }
39   switch (type) {
40   case "squre":
41     return {(num:Int) -> Int in
42         return num * num
43      }
44   default:
45     return {(num:Int) -> Int in
46        return num * num * num
47     }
48   }
49 }
50 var maxFunc3 = getMathFunc("squre")
51 maxFunc3(5)
52 var maxFunc4 = getMathFunc("other")
53 maxFunc4(5)
54 
55 //
56 var squre: (Int) -> Int = {(num) in return num * num}
57 squre(3)
58 
59 
60 //?? 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
61 var a:Int?
62 //a = 11
63 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() { }
}