19.Swift学习之构造函数与析构函数

init() {
    // perform some initialization here
}

class Person: NSObject {
    var name : String
    var age : Int

    // 重写了NSObject(父类)的构造方法
    override init() {
        name = ""
        age = 0
    }
}

// 创建一个Person对象
let p = Person()

class Person: NSObject {
    var name : String
    var age : Int

    // 自定义构造函数,会覆盖init()函数
    init(name : String, age : Int) {
        self.name = name
        self.age = age
    }
}

// 创建一个Person对象
let p = Person(name: "why", age: 18)

//定义了一个名为 Size 有两个属性分别是 width 和 height 的结构体，这两个属性通过分配默认值 0.0 ，从而被推断为 Double 类型
struct Size {
    var width = 0.0, height = 0.0
}
//Size 结构体自动接收一个 init(width:heght:) 构造函数
let twoByTwo = Size(width: 2.0, height: 2.0)

//类的指定构造函数
init(parameters) {
    statements
}
//便捷构造函数有着相同的书写方式，但是要用 convenience 修饰符放到 init 关键字前，用空格隔开：
convenience init(parameters) {
    statements
}

class Person {   
    var name: String!
    var weight: Double  
    init(name: String) {
        self.name = name
        self.weight = 0.0
    } 
    // 定义指定构造器
    init(name: String, weight: Double) {
        self.name = name
        self.weight = weight
    }
     
    // 定义便利构造器(使用convenience修饰)
    convenience init(n name: String, w weight: Double) {
        // 便利构造器必须调用同类中的指定构造器
        self.init(name: name, weight: weight)
    }
     
    convenience init(showStr: String) {
        self.init(name: "", weight: 0.0)
        print(showStr)
    }
}
 
class Man: Person {
    var sex: String = "男"   
    override init(name: String) {
        // 子类的指定构造器中必须调用父类的指定构造器
        super.init(name: name)
        self.name = name
        self.weight = 0.0
    }
    override init(name: String, weight: Double) {
        super.init(name: name, weight: weight)
        self.name = name
        self.weight = weight
    }   
    // 定义指定构造器与父类的便利构造器一样, 这里不算重写
    convenience init(showStr: String) {
        self.init(name: "", weight: 0.0)
        print(showStr)
    }
}
 
var manA = Man(name: "ZhangSan", weight: 62.0)
var manB = Man(showStr: "Hello Swift")

struct Animal {
    let species: String
    init?(species: String) {
        if species.isEmpty { return nil }
        self.species = species
    }
}
let someCreature = Animal(species: "Giraffe")
if let giraffe = someCreature {
    print("An animal was initialized with a species of \(giraffe.species)")
}

class SomeClass {
    required init() {
    }
}

class SomeSubclass: SomeClass {
    required init() {
    }
}

deinit {
    // 执行析构过程
}

class Person {
    var name : String
    var age : Int

    init(name : String, age : Int) {
        self.name = name
        self.age = age
    }

    deinit {
        print("Person-deinit")
    }
}

var p : Person? = Person(name: "why", age: 18)
p = nil