Swift初始化器与可选链的使用方法介绍

class Person {
    required init() {}
    init(age: Int) {}
}
class Student: Person {
    init(no: Int) {
        super.init(age: 0)
    }
    required init() {
        super.init()
    }
}

class Person {
    var age: Int {
        willSet {
            print("willSet", newValue)
        }
        didSet {
            print("didSet", oldValue, age)
        }
    }
    init() {
        self.age = 0
    }
}
class Student: Person {
    override init() {
        super.init()
        self.age = 1
    }
}

class Person {
    var name: String
    init?(name: String) {
        if name.isEmpty {
            return nil
        }
        self.name = name
    }
}

class Person {
    var name: String
    init?(name: String) {
        if name.isEmpty {
            return nil
        }
        self.name = name
    }
    convenience init() {
        self.init(name: "")!
    }
}

class Person {
    deinit {
        print("Person对象销毁了")
    }
}

class Car {
    var price = 0
}
class Dog {
    var weight = 0
}
class Person {
    var name: String = ""
    var dog: Dog = Dog()
    var car: Car? = Car()
    func age() -> Int {
        18
    }
    func eat() {
        print("Person eat")
    }
    subscript(index: Int) -> Int {
        return index
    }
}
var person: Person? = Person()
var age = person?.age()//Int? Optional(18)
var age1 = person!.age() // Int
var name = person?.name //String?
var index = person?[6] // Int?

if let age = person?.age() { // ()?
    print("调用age成功", age)
} else {
    print("调用age失败")
}

var dog = person?.dog // Dog?
var weight = person?.dog.weight // Int?
var price = person?.car?.price // Int?

var scores = [
    "Jack" : [86, 82, 84],
    "Rose" : [79, 94, 81]
]
scores["Jack"]?[0] = 100
scores["Rose"]?[2] += 10
scores["Kate"]?[0] = 88

var num1: Int? = 5
num1? = 10 // Optional(10)
var num2: Int? = nil
num2? = 10 // nil

var dict: [String : (Int, Int) -> Int] = [
    "sum" : (+), //两个Int类型相加，返回一个Int类型
    "difference" : (-)
]
var result = dict["sum"]?(10, 20) // Optional(30), Int?