swift入门第三季（枚举，类，面向对象, 协议）

枚举

枚举形式：

enum 枚举名{
//使用case关键字列出所有枚举值
}

关联值：

enum plant{
case Eerth(weight:Double,name:String)
}

类

class User {
//存储属性
var first: String = "";
var last: String = "";
//计算属性
var fullName: String {
get{
return first + "-" + last;
}
set(newValue){
var names = newValue.components(separatedBy: "-");
self.first = names[0];
self.last = names[1];
}
}
//构造器
init(first:String, last:String) {
self.first = first;
self.last = last;
}
}
let s = User(first: "极客", last: "Hello");
print(s.fullName)
s.fullName = "测试-测试2"
print(s.fullName)

属性观察器

class Person {
var age: Int = 0 {
willSet {
if newValue < 0 || newValue > 200 {
print("年龄\(newValue)设置不符合要求，请重新设置！")
}else {
print("年龄设置符合要求，设置成功")
}
}
didSet {
print("年龄设置完成，被修改的年龄为:\(oldValue)")
}
}
}
var p = Person();
p.age = 220;

两种类中的方法，实例方法和类型方法

class SomeClass {
func test() {
print("==test 方法 ==")
}
class func bar(Msg msg:String) {
print("==bar类型方法==，传入的参数是:\(msg)")
}
}
var sc = SomeClass()
var f1:()->() = sc.test;//通过对象进行调用
var f2:(String)->Void = SomeClass.bar//通过类进行调用
f1()
f2("极客")

方法有多个参数的，除第一个外，其他都要带参数名调用。

如果不想要带参数名，可以使用_修饰参数名

可变方法，mutating

struct JKRect {
var x:Int
var y:Int
var width:Int
var height:Int
mutating func moveByX(x:Int,y:Int) {
self.x += x
self.y += y
}
}
var rect = JKRect(x: 20, y: 12, width:200, height: 300)
rect.moveByX(x: 100, y: 90)
print("rect矩形的左上角的x坐标为：\(rect.x),y坐标为：\(rect.y)")

下标，用subscript修饰

struct JKRect {
var x:Int
var y:Int
var width:Int
var height:Int
subscript (index: Int) -> Int {
get{
switch(index) {
case 0:
return self.x
case 1:
return self.y
case 2:
return self.width
case 3:
return self.height
default:
print("不支持该索引值")
return 0
}
}
set{
switch(index) {
case 0:
self.x = newValue
case 1:
self.y = newValue
case 2:
self.width = newValue
case 3:
self.height = newValue
default:
print("不支持该索引值")
}
}
}
}
var rect2 = JKRect(x: 20, y: 12, width:200, height: 300)
print("rect矩形的左上角的x坐标为：\(rect2.x),y坐标为：\(rect2.y)")

可选链

class Customer{
var name=""
var emp:Employee?
init(name:String) {
self.name = name
}
}

class Company{
var name = ""
var addr = ""
init(name:String,addr:String) {
self.name = name
self.addr = addr
}
}

class Employee{
var name = "Lily"
var title = "行政"
var company:Company! //不需要强制解析
init(name:String,title:String) {
self.name = name
self.title = title
}
func  info() {
print("本员工名为\(self.name),职位是\(self.title))")
}
}
//第一种方式
//var c = Customer(name:"Damon")
//var emp = Employee(name:"Elena",title:"Student")
//c.emp = emp;
//emp.company = Company(name:"极客学院",addr:"北京市")
//print("为\(c.name)服务的公司名为\(c.emp!.company.name)")

//第二种方式 (单独使用第二种会崩溃，因为company没有值)
var c2 = Customer(name: "Lucky")
c2.emp = Employee(name: "Snow", title:"客服")
//print("为\(c2.name)服务的公司名为\(c2.emp!.company.name)") 这样会崩溃
print("为\(c2.name)服务的公司名为\(c2.emp?.company?.name)")//用可选链

static 在枚举，结构体中修饰的属性和方法

class 在类中修饰的属性和方法

结构体可以包含实例计算属性，不能包含实例存储属性

类中不能定义类型存储属性，只能包含类型计算属性

构造器中常量属性可以修改

可能失败的构造器

struct cat {
let name:String
init?(name:String) {
if name.isEmpty {
return nil
}
self.name = name
}
}
let c1 = cat(name:"Kitty")
if c1 != nil {
print("C1的name为：\(c1!.name)")
}
let c2 = cat(name: "")
print(c2)

AnyObject: 可代表任何类的实例

Any:代表任何类

协议：类似于其他语言的接口（多继承）

protocol Strokable{
var strokeWidth:Double {get set}
}

protocol Fullable {
var fullColor: Color?{get set}
}

enum Color{
case Red,Green,Blue,Yellow,Cyan
}

protocol HasArea : Fullable,Strokable {
var area: Double {get}
}

protocol Mathable {
static var pi:Double {get}
static var e:Double {get}
}

struct Rect:HasArea,Mathable{
var width:Double
var height:Double
init(width:Double,height:Double) {
self.width = width
self.height = height
}
var fullColor: Color?
var strokeWidth: Double = 0.0
var area: Double {
get{
return width*height
}
}
static var pi:Double = 3.14159535
static var e:Double = 2.71828
}