Swift编程中的初始化与反初始化完全讲解

init()
{
    //New Instance initialization goes here
}

struct rectangle {
    var length: Double
    var breadth: Double
    init() {
        length = 6
        breadth = 12
    }
}
var area = rectangle()
println("area of rectangle is \(area.length*area.breadth)")

struct rectangle {
    var length = 6
    var breadth = 12
}
var area = rectangle()
println("area of rectangle is \(area.length*area.breadth)")

struct Rectangle {
    var length: Double
    var breadth: Double
    var area: Double
   
    init(fromLength length: Double, fromBreadth breadth: Double) {
        self.length = length
        self.breadth = breadth
        area = length * breadth
    }
   
    init(fromLeng leng: Double, fromBread bread: Double) {
        self.length = leng
        self.breadth = bread
        area = leng * bread
    }
}

let ar = Rectangle(fromLength: 6, fromBreadth: 12)
println("area is: \(ar.area)")

let are = Rectangle(fromLeng: 36, fromBread: 12)
println("area is: \(are.area)")

struct Days {
    let sunday, monday, tuesday: Int
    init(sunday: Int, monday: Int, tuesday: Int) {
        self.sunday = sunday
        self.monday = monday
        self.tuesday = tuesday
    }
   
    init(daysofaweek: Int) {
        sunday = daysofaweek
        monday = daysofaweek
        tuesday = daysofaweek
    }
}

let week = Days(sunday: 1, monday: 2, tuesday: 3)
println("Days of a Week is: \(week.sunday)")
println("Days of a Week is: \(week.monday)")
println("Days of a Week is: \(week.tuesday)")

let weekdays = Days(daysofaweek: 4)
println("Days of a Week is: \(weekdays.sunday)")
println("Days of a Week is: \(weekdays.monday)")
println("Days of a Week is: \(weekdays.tuesday)")

 

struct Rectangle {
    var length: Double
   
    init(frombreadth breadth: Double) {
        length = breadth * 10
    }
   
    init(frombre bre: Double) {
        length = bre * 30
    }
   
    init(_ area: Double) {
        length = area
    }
}

let rectarea = Rectangle(180.0)
println("area is: \(rectarea.length)")

let rearea = Rectangle(370.0)
println("area is: \(rearea.length)")

let recarea = Rectangle(110.0)
println("area is: \(recarea.length)")

struct Rectangle {
    var length: Double?
   
    init(frombreadth breadth: Double) {
        length = breadth * 10
    }
   
    init(frombre bre: Double) {
        length = bre * 30
    }
   
    init(_ area: Double) {
        length = area
    }
}

let rectarea = Rectangle(180.0)
println("area is: \(rectarea.length)")

let rearea = Rectangle(370.0)
println("area is: \(rearea.length)")

let recarea = Rectangle(110.0)
println("area is: \(recarea.length)")

struct Rectangle {
    let length: Double?
   
    init(frombreadth breadth: Double) {
        length = breadth * 10
    }
   
    init(frombre bre: Double) {
        length = bre * 30
    }
   
    init(_ area: Double) {
        length = area
    }
}

let rectarea = Rectangle(180.0)
println("area is: \(rectarea.length)")

let rearea = Rectangle(370.0)
println("area is: \(rearea.length)")

let recarea = Rectangle(110.0)
println("area is: \(recarea.length)")

class defaultexample {
    var studname: String?
    var stmark = 98
    var pass = true
}
var result = defaultexample()

println("result is: \(result.studname)")
println("result is: \(result.stmark)")
println("result is: \(result.pass)")

struct Rectangle {
    var length = 100.0, breadth = 200.0
}
let area = Rectangle(length: 24.0, breadth: 32.0)

println("Area of rectangle is: \(area.length)")
println("Area of rectangle is: \(area.breadth)")

struct Stmark {
    var mark1 = 0.0, mark2 = 0.0
}
struct stdb {
    var m1 = 0.0, m2 = 0.0
}

struct block {
    var average = stdb()
    var result = Stmark()
   
    init() {}
   
    init(average: stdb, result: Stmark) {
        self.average = average
        self.result = result
    }
   
    init(avg: stdb, result: Stmark) {
        let tot = avg.m1 - (result.mark1 / 2)
        let tot1 = avg.m2 - (result.mark2 / 2)
        self.init(average: stdb(m1: tot, m2: tot1), result: result)
    }
}

let set1 = block()
println("student result is: \(set1.average.m1, set1.average.m2) \(set1.result.mark1, set1.result.mark2)")

let set2 = block(average: stdb(m1: 2.0, m2: 2.0),
    result: Stmark(mark1: 5.0, mark2: 5.0))
println("student result is: \(set2.average.m1, set2.average.m2) \(set2.result.mark1, set2.result.mark2)")

let set3 = block(avg: stdb(m1: 4.0, m2: 4.0),
    result: Stmark(mark1: 3.0, mark2: 3.0))
println("student result is: \(set3.average.m1, set3.average.m2) \(set3.result.mark1, set3.result.mark2)")

 

class mainClass {
    var no1 : Int // local storage
    init(no1 : Int) {
        self.no1 = no1 // initialization
    }
}
class subClass : mainClass {
    var no2 : Int // new subclass storage
    init(no1 : Int, no2 : Int) {
        self.no2 = no2 // initialization
        super.init(no1:no1) // redirect to superclass
    }
}

let res = mainClass(no1: 10)
let print = subClass(no1: 10, no2: 20)

println("res is: \(res.no1)")
println("res is: \(print.no1)")
println("res is: \(print.no2)")

class mainClass {
    var no1 : Int // local storage
    init(no1 : Int) {
        self.no1 = no1 // initialization
    }
}

class subClass : mainClass {
    var no2 : Int
    init(no1 : Int, no2 : Int) {
        self.no2 = no2
        super.init(no1:no1)
    }
    // Requires only one parameter for convenient method
    override convenience init(no1: Int)  {
        self.init(no1:no1, no2:0)
    }
}
let res = mainClass(no1: 20)
let print = subClass(no1: 30, no2: 50)

println("res is: \(res.no1)")
println("res is: \(print.no1)")
println("res is: \(print.no2)")

class sides {
    var corners = 4
    var description: String {
        return "\(corners) sides"
    }
}
let rectangle = sides()
println("Rectangle: \(rectangle.description)")

class pentagon: sides {
    override init() {
        super.init()
        corners = 5
    }
}

let bicycle = pentagon()
println("Pentagon: \(bicycle.description)")

class Planet {
    var name: String
   
    init(name: String) {
        self.name = name
    }
   
    convenience init() {
        self.init(name: "[No Planets]")
    }
}
let plName = Planet(name: "Mercury")
println("Planet name is: \(plName.name)")

let noplName = Planet()
println("No Planets like that: \(noplName.name)")

class planets: Planet {
    var count: Int
    init(name: String, count: Int) {
        self.count = count
        super.init(name: name)
    }
   
    override convenience init(name: String) {
        self.init(name: name, count: 1)
    }
}

struct studrecord {
    let stname: String
   
    init?(stname: String) {
        if stname.isEmpty {return nil }
        self.stname = stname
    }
}

let stmark = studrecord(stname: "Swing")
if let name = stmark {
    println("Student name is specified")
}

let blankname = studrecord(stname: "")
if blankname == nil {
    println("Student name is left blank")
}

enum functions {
    case a, b, c, d
    init?(funct: String) {
        switch funct {
        case "one":
            self = .a
        case "two":
            self = .b
        case "three":
            self = .c
        case "four":
            self = .d
        default:
            return nil
        }
    }
}

let result = functions(funct: "two")
if result != nil {
    println("With In Block Two")
}

let badresult = functions(funct: "five")
if badresult == nil {
    println("Block Does Not Exist")
}

class studrecord {
    let studname: String!
    init?(studname: String) {
        self.studname = studname
        if studname.isEmpty { return nil }
    }
}
if let stname = studrecord(studname: "Failable Initializers") {
    println("Module is \(stname.studname)")
}

class Planet {
    var name: String
   
    init(name: String) {
        self.name = name
    }
   
    convenience init() {
        self.init(name: "[No Planets]")
    }
}
let plName = Planet(name: "Mercury")
println("Planet name is: \(plName.name)")

let noplName = Planet()
println("No Planets like that: \(noplName.name)")

class planets: Planet {
    var count: Int
   
    init(name: String, count: Int) {
        self.count = count
        super.init(name: name)
    }
   
    override convenience init(name: String) {
        self.init(name: name, count: 1)
    }
}

struct studrecord {
    let stname: String
   
    init!(stname: String) {
        if stname.isEmpty {return nil }
        self.stname = stname
    }
}

let stmark = studrecord(stname: "Swing")
if let name = stmark {
    println("Student name is specified")
}

let blankname = studrecord(stname: "")
if blankname == nil {
    println("Student name is left blank")
}

 class classA {
    required init() {
        var a = 10
        println(a)
    }
}

class classB: classA {
    required init() {
        var b = 30
        println(b)
    }
}
let res = classA()
let print = classB()

var counter = 0;  // for reference counting
class baseclass {
    init() {
        counter++;
    }
    deinit {
        counter--;
    }
}

var print: baseclass? = baseclass()
println(counter)
print = nil
println(counter)

var counter = 0;  // for reference counting

class baseclass {
    init() {
        counter++;
    }
   
    deinit {
        counter--;
    }
}

var print: baseclass? = baseclass()

println(counter)
println(counter)