協(xié)議(Protocol)
????協(xié)議可以用來定義方法乾蓬、屬性施戴、下標(biāo)的聲明纸俭，協(xié)議可以被枚舉皇耗、結(jié)構(gòu)體、類遵守(多個(gè)協(xié)議之間用逗號(hào)隔開)
protocol Drawable {
? ? func draw()
? ? var x: Int { get set }
? ? var y: Int { get }
? ? subscript(index: Int) -> Int { get set }
}
protocol Test1 {}
protocol Test2 {}
protocol Test3 {}
class TestClass : Test1, Test2, Test3 {}
????協(xié)議中定義方法時(shí)不能有默認(rèn)參數(shù)值
????默認(rèn)情況下揍很，協(xié)議中定義的內(nèi)容必須全部都實(shí)現(xiàn)?
????也有辦法辦到只實(shí)現(xiàn)部分內(nèi)容郎楼，以后會(huì)講到
協(xié)議中的屬性
protocol Drawable {? ? func draw()
????var?x:?Int?{?get set?}
????var?y:?Int?{?get?}
????subscript(index:?Int) ->?Int?{?get set?}
}
協(xié)議中定義屬性時(shí)必須用var關(guān)鍵字
實(shí)現(xiàn)協(xié)議時(shí)的屬性權(quán)限要不小于協(xié)議中定義的屬性權(quán)限
協(xié)議定義get万伤、set，用var存儲(chǔ)屬性或get呜袁、set計(jì)算屬性去實(shí)現(xiàn)?
協(xié)議定義get敌买，用任何屬性都可以實(shí)現(xiàn)
class Person : Drawable {? ? var x: Int = 0
? ? let y: Int = 0? ? func draw() {
? ? ? ? print("Person draw")
? ? }
????subscript(index:?Int) ->?Int?{?set?{}
????get?{ index } }
}
class Person : Drawable {? ??
????var x: Int {
????????get?{?0?}
????????set?{} }
????var?y:?Int?{?0?}
????func?draw() {?print("Person draw") }?
????subscript(index:?Int) ->?Int?{
????????set?{}
????????get?{ index } }
}
static、class
????為了保證通用阶界，協(xié)議中必須用static定義類型方法虹钮、類型屬性、類型下標(biāo)
protocol Drawable {
? ? static func draw()
}
class Person1 : Drawable {
? ? class func draw() {
? ? ? ? print("Person1 draw")
? ? }
}
class Person2 : Drawable {
? ? static func draw() {
? ? ? ? print("Person2 draw")
? ? }
}
mutating
????只有將協(xié)議中的實(shí)例方法標(biāo)記為mutating才允許結(jié)構(gòu)體膘融、枚舉的具體實(shí)現(xiàn)修改自身內(nèi)存
????類在實(shí)現(xiàn)方法時(shí)不用加mutating芙粱，枚舉、結(jié)構(gòu)體才需要加mutating
protocol Drawable {
? ? mutating func draw()
}
class Size : Drawable {
? ? var width: Int = 0
? ? func draw() {
width = 10 }
}
struct Point : Drawable {
? ? var x: Int = 0
? ? mutating func draw() {
? ? ? ? x = 10
} }
init
????協(xié)議中還可以定義初始化器init?
????非final類實(shí)現(xiàn)時(shí)必須加上required?
protocol Drawable {
? ? init(x: Int, y: Int)
}
class Point : Drawable {
? ? required init(x: Int, y: Int) {}
}
final class Size : Drawable {
? ? init(x: Int, y: Int) {}
}
????如果從協(xié)議實(shí)現(xiàn)的初始化器托启，剛好是重寫了父類的指定初始化器?
????那么這個(gè)初始化必須同時(shí)加required宅倒、override ? ?
protocol Livable {
? ? init(age: Int)
}
class Person {
? ? init(age: Int) {}
}
class Student : Person, Livable {
? ? required override init(age: Int) {
? ? ? ? super.init(age: age)
? ? }
}
init、init?屯耸、init!
????協(xié)議中定義的init?拐迁、init!，可以用init疗绣、init?线召、init!去實(shí)現(xiàn)?
????協(xié)議中定義的init，可以用init多矮、init!去實(shí)現(xiàn)
? protocol Livable {
? ? init()
? ? init?(age: Int)
? ? init!(no: Int)
}
class Person : Livable {
? ? required init() {}
? ? // required init!() {}
? ? required init?(age: Int) {}
? ? // required init!(age: Int) {}
? ? // required init(age: Int) {}
? ? required init!(no: Int) {}
? ? // required init?(no: Int) {}
? ? // required init(no: Int) {}
}
協(xié)議的繼承
????一個(gè)協(xié)議可以繼承其他協(xié)議
protocol Runnable {
? ? func run()
}
protocol Livable : Runnable {
? ? func breath()
}
class Person : Livable {
? ? func breath() {}
? ? func run() {}
}
協(xié)議組合
protocol Livable {}
protocol Runnable {}
class Person {}
協(xié)議組合缓淹，可以包含1個(gè)類類型(最多1個(gè))
// 接收Person或者其子類的實(shí)例
func fn0(obj: Person) {}
// 接收遵守Livable協(xié)議的實(shí)例
func fn1(obj: Livable) {}
// 接收同時(shí)遵守Livable、Runnable協(xié)議的實(shí)例
func fn2(obj: Livable & Runnable) {}
// 接收同時(shí)遵守Livable塔逃、Runnable協(xié)議讯壶、并且是Person或者其子類的實(shí)例 func fn3(obj: Person & Livable & Runnable) {}
typealias RealPerson = Person & Livable & Runnable
// 接收同時(shí)遵守Livable、Runnable協(xié)議湾盗、并且是Person或者其子類的實(shí)例 func fn4(obj: RealPerson) {}
CaseIterable
????讓枚舉遵守CaseIterable協(xié)議伏蚊，可以實(shí)現(xiàn)遍歷枚舉值
enum Season : CaseIterable {
? ? case spring, summer, autumn, winter
}
let seasons = Season.allCases
print(seasons.count) // 4
for season in seasons {
? ? print(season)
} // spring summer autumn winter
CustomStringConvertible
????遵守CustomStringConvertible、 CustomDebugStringConvertible協(xié)議格粪，都可以自定義實(shí)例的打印字符串
class Person : CustomStringConvertible, CustomDebugStringConvertible {?
????var age = 0
????var description: String { "person_\(age)" }
????var debugDescription: String { "debug_person_\(age)" } }
????var person = Person()
????print(person) // person_0?
????debugPrint(person) // debug_person_0
print調(diào)用的是CustomStringConvertible協(xié)議的description
debugPrint躏吊、po調(diào)用的是CustomDebugStringConvertible協(xié)議的debugDescription
Any、AnyObject
????Swift提供了2種特殊的類型:Any帐萎、AnyObject?
????????Any:可以代表任意類型(枚舉比伏、結(jié)構(gòu)體、類疆导，也包括函數(shù)類型)?
????????AnyObject:可以代表任意類類型(在協(xié)議后面寫上: AnyObject代表只有類能遵守這個(gè)協(xié)議)?
????在協(xié)議后面寫上: class也代表只有類能遵守這個(gè)協(xié)議
var stu: Any = 10
stu = "Jack"
stu = Student()
// 創(chuàng)建1個(gè)能存放任意類型的數(shù)組 //?
var data = Array<Any>()?
var data = [Any]()?
data.append(1)?
data.append(3.14)?
data.append(Student())?
data.append("Jack")?
data.append({ 10 })
is赁项、as?、as!、as
????is用來判斷是否為某種類型肤舞，as用來做強(qiáng)制類型轉(zhuǎn)換
protocol Runnable { func run() }?
class Person {}
class Student : Person, Runnable {
? ? func run() {
? ? ? ? print("Student run")
? ? }
? ? func study() {
? ? ? ? print("Student study")
? ? }
}
var stu: Any = 10
(stu as? Student)?.study() // 沒有調(diào)用study stu = Student()
(stu as? Student)?.study() // Student study (stu as! Student).study() // Student study (stu as? Runnable)?.run() // Student run
var data = [Any]() data.append(Int("123") as Any)
var d = 10 as Double
print(d) // 10.0
var stu: Any = 10
print(stu is Int) // true
stu = "Jack"
print(stu is String) // true stu = Student()
print(stu is Person) // true print(stu is Student) // true print(stu is Runnable) // true
X.self紫新、X.Type、AnyClass
????X.self是一個(gè)元類型(metadata)的指針李剖，metadata存放著類型相關(guān)信息 n X.self屬于X.Type類型
class Person {}
class Student : Person {}
var perType: Person.Type = Person.self var stuType: Student.Type = Student.self perType = Student.self
----------
var anyType: AnyObject.Type = Person.self?
anyType = Student.self
public typealias AnyClass = AnyObject.Type?
var anyType2: AnyClass = Person.self?
anyType2 = Student.self
---------
var per = Person()
var perType = type(of: per) // Person.self print(Person.self == type(of: per)) // true
元類型的應(yīng)用
class Animal { required init() {} } class Cat : Animal {}
class Dog : Animal {}
class Pig : Animal {}
func create(_ clses: [Animal.Type]) -> [Animal] {?
????var arr = [Animal]()
? ? for cls in clses {
????????arr.append(cls.init()) }
????????return arr }
print(create([Cat.self, Dog.self, Pig.self]))
--------------------------
import Foundation
class Person {
? ? var age: Int = 0
}
class Student : Person {
? ? var no: Int = 0
}
print(class_getInstanceSize(Student.self)) // 32 print(class_getSuperclass(Student.self)!) // Person print(class_getSuperclass(Person.self)!) // Swift._SwiftObject
從結(jié)果可以看得出來芒率，Swift還有個(gè)隱藏的基類:Swift._SwiftObject?
可以參考Swift源碼:https://github.com/apple/swift/blob/master/stdlib/public/runtime/SwiftObject.h
Self
Self代表當(dāng)前類型
class Person {
? ? var age = 1
? ? static var count = 2
? ? func run() {
? ? ? ? print(self.age) // 1
? ? ? ? print(Self.count) // 2
? ? }
}
Self一般用作返回值類型，限定返回值跟方法調(diào)用者必須是同一類型(也可以作為參數(shù)類型)
? protocol Runnable {
? ? func test() -> Self
}
class Person : Runnable {
? ? required init() {}
????func test() -> Self { type(of: self).init() }?
}
class Student : Person {}
var p = Person()
// Person
print(p.test())
var stu = Student()
// Student
print(stu.test())
