swift系统学习第三章

第九节:结构体-sturt

 1 //: Playground - noun: a place where people can play
 2 
 3 import UIKit
 4 
 5 /*
 6 swift学习第九节
 7 结构体:sturt
 8 */
 9 let centerX = 100.0
10 let centerY = 100.0
11 let distance = 200.0
12 //定义结构体sturt
13 struct Location {
14     var x : Double = 100
15     var y : Double = 200
16     
17     //结构体初始化
18     init (StringPoint:String){
19        let xy = StringPoint.characters.split(",")
20         x = atof(String(xy.first!))
21         y = atof(String(xy.last!))
22        
23     }
24     init(x:Double,y:Double){
25        self.x = x
26        self.y = y
27     }
28     init(){}
29     
30     mutating func move2(dist:Double){
31        self.x += dist
32         
33     }
34     
35 }
36 
37 var pointA = Location(x: 100, y: 200)
38 let pointB = Location(StringPoint: "100,200")
39 let PointC = Location()
40 pointA.x
41 pointA.y
42 pointB.x
43 pointB.y
44 
45 //把结构体作为参数传入
46 func inRange(point:Location) -> Bool {
47    let distX = point.x - centerX
48    let distY = point.y - centerY
49    let dist = sqrt(pow(distX, 2) + pow(distY,2))
50    return dist < distance
51 }
52 inRange(pointA)
53 
54 func move(dist:Double,inout point:Location){
55    point.x += dist
56 }
57 move(100, point: &pointA)
58 pointA
59 pointA.move2(100.0)
60 
61 //extension 扩展
62 extension Location {
63     mutating func move3(dist:Double){
64        self.y += y
65     }
66 }
67 pointA.move3(100)
68 
69 extension String {
70     func isEven() -> Bool {
71         return self.characters.count % 2 == 0 ? true : false
72     }
73 }
74 "An even string".isEven()
75 
76 var copyPointA = pointA
77 copyPointA.y = 10000.0
78 pointA    // struct 是值类型

第十节:
struct 和 class
       1. class 必须有init()方法
          struct 可以不写init()方法,默认有init方法
       2. struct 为值类型
          class 为引用类型

 1 //: Playground - noun: a place where people can play
 2 /*
 3 swift学习第十节
 4 struct 和 class
 5        1. class 必须有init()方法
 6           struct 可以不写init()方法,默认有init方法
 7        2. struct 为值类型
 8           class 为引用类型
 9 
10 */
11 import UIKit
12 
13 struct PointVal {
14     var x: Int
15     var y: Int
16     init(x:Int,y:Int){
17        self.x = x
18        self.y = y
19     }
20     mutating func moveX(x:Int){
21       self.x += x
22     }
23 }
24 class PointRef {
25     var x: Int
26     var y: Int
27     init(x:Int,y:Int){
28         self.x = x
29         self.y = y
30     }
31     func moveX(x:Int){
32       self.x += x
33     }
34 }
35 let p1 = PointVal(x: 0, y: 1)
36 let p2 = PointRef(x: 0, y: 2)
37 let p3 = PointRef(x: 0, y: 2)
38 // p1.x = 10
39 p2.x = 10    //这里,p1不能修改,但是p2可以修改.因为p2是引用类型,p1是值类型
40 if p2 === p3 {
41    print("他们是相同的对象")
42 }
43 if p2 !== p3{
44    print("他们不是相同的对象")
45 }
46 
47 var p4 = p1
48 p4.x = 10
49 p1.x
50 
51 var p5 = p2
52 p5.x = 10
53 p2.x

第十一节:
函数式
内存泄露:循环引用

 1 //: Playground - noun: a place where people can play
 2 
 3 import UIKit
 4 /*
 5 swift学习第十一节
 6 函数式
 7 内存泄露:循环引用
 8 
 9 */
10 var number = [1,2,3,4,5,6]
11 var event = [Int]()
12 for n in number {
13     if n % 2 == 0{
14        event.append(n)
15     }
16 }
17 event
18 
19 let evens1 = number.filter({(n:Int) -> Bool in return n % 2 == 0})
20 evens1
21 
22 //-------------------------------内存管理--------------------
23 class Person {
24     let name:String
25     init(name:String){
26        self.name = name
27        print("\(name) 被构建")
28     }
29     deinit{
30        print("\(name) 被销毁")
31     }
32 }
33 var ref1:Person?
34 var ref2:Person?
35 
36 ref1 = Person(name: "Tom")   //Person对象的引用计数为1
37 ref2 = ref1                //Person对象的引用计数为2
38 ref1 = nil                 //Person对象的引用计数为1
39 ref2 = nil                 //deinit()方法被执行
40 
41 //循环引用造成的内存泄露
42 class Student {
43     let name:String
44     var apartment:School?
45     init(name:String){
46        self.name = name
47         print("\(name)被创建")
48     }
49     deinit{
50         print("\(name)被销毁");
51     }
52 }
53 class School {
54     let unit: String
55     var tenant: Student?
56     init(unit:String){
57       self.unit = unit
58       print("\(unit)被创建")
59     }
60     deinit{
61        print("\(unit)被销毁")
62     }
63 }
64 var tom:Student? = Student(name: "TOM")
65 var apt11:School? = School(unit: "11")
66 
67 //tom!.apartment = apt11   //这两句会造成循环引用
68 //apt11!.tenant  = tom
69 
70 tom = nil
71 apt11 = nil

第十二节:

reference cycle 的方式
1.使用weak   使用weak,不会造成引用计数+1,如果没有指向任何对象,则自动设置为nil
   场景:双方均可以为空
2.umowned
   场景:一方可以为空

 1 //: Playground - noun: a place where people can play
 2 /*
 3 reference cycle 的方式
 4 1.使用weak   使用weak,不会造成引用计数+1,如果没有指向任何对象,则自动设置为nil
 5    场景:双方均可以为空
 6 2.umowned
 7    场景:一方可以为空
 8 
 9 */
10 
11 
12 import UIKit
13 
14 //循环引用造成的内存泄露
15 class Student {
16     let name:String
17     var apartment:School?
18     init(name:String){
19         self.name = name
20         print("\(name)被创建")
21     }
22     deinit{
23         print("\(name)被销毁");
24     }
25 }
26 class School {
27     let unit: String
28     weak  var tenant: Student?
29     init(unit:String){
30         self.unit = unit
31         print("\(unit)被创建")
32     }
33     deinit{
34         print("\(unit)被销毁")
35     }
36 }
37 var tom:Student? = Student(name: "TOM")
38 var apt11:School? = School(unit: "11")
39 
40 tom!.apartment = apt11   //这两句会造成循环引用
41 apt11!.tenant  = tom
42 
43 tom = nil
44 apt11 = nil