結(jié)構(gòu)體
- 在swift 標(biāo)準(zhǔn)庫中，絕大多數(shù)的公開類型都是結(jié)構(gòu)體泻骤，而枚舉和類只占很小一部分
- 比如Bool、int梧奢、double狱掂、string、array亲轨、dictionary等常見類型都是結(jié)構(gòu)體
struct Data {
var year: Int
var month: Int
var day: Int
}
//調(diào)用趋惨，可以傳入所有的成員值，用以初始化所有成員（存儲屬性）
var data = Data(year: 2021, month: 2, day: 23)
- 所有結(jié)構(gòu)體都有一個編譯器生成的初始化器（initializer,初始化方法惦蚊，構(gòu)造器希柿，構(gòu)造方法）
自定義初始化器
- 一旦在定義結(jié)構(gòu)體是自定義了初始化器诊沪，編譯器就不會再自動生成其他的初始化器
struct Point {
var x: Int = 0
var y: Int = 0
init(x: Int, y: Int) {
self.x = x
self.y = y
}
}
var p1 = Point(x: 10, y: 10)
類
- 類的定義和結(jié)構(gòu)體類似，但是編譯器并沒有為類自動生成可以傳入成員值的初始化器
class Point {
var x: Int = 0
var y: Int = 0
}
let p1 = Point()
let p2 = Point(x: 10, y: 20) //報錯
let p3 = Point(x: 10) //報錯
類的初始化器
- 如果類的所有成員都在定義的時候指定了初始化值曾撤，編譯器會為類生成無參的初始化器
- 成員的初始化是在這個初始化器中完成的
class Point {
var x: Int = 0
var y: Int = 0
}
let p1 = Point()
||
class Point {
var x: Int = 0
var y: Int = 0
init() {
x = 10
y = 20
}
}
let p1 = Point()
結(jié)構(gòu)體和類的本質(zhì)區(qū)別
- 結(jié)構(gòu)體是值類型（枚舉也是值類型）端姚，類是引用類型（指針類型）
class Size { struct Point {
//創(chuàng)建類的實例對象需要向堆空間申請內(nèi)存
var width = 1 var x = 3
var height = 2 var y = 4
} }
值類型
- 值類型賦值給var、let或者給函數(shù)傳值挤悉，是直接將所有內(nèi)容拷貝一份
- 類似將文件進(jìn)行copy渐裸、paste操作，產(chǎn)生了全新的文件副本装悲。屬于深拷貝
struct Point {
var x: Int
var y: Int
}
func test() {
var p1 = Point(x: 10, y: 20)
var p2 = p1
}
值類型的復(fù)制操作
//字符串
var s1 = "jack"
var s2 = s1
s2.append("_Rose")
print(s1)// jack
print(s2)// jack_Rose
//數(shù)組
var a1 = [1, 2, 3]
var a2 = a1
a1[0] = 2
a2.append(4)
print(a1)// [2, 2, 3]
print(a2) //[1, 2, 3, 4]
//字典
var d1 = ["max" : 10, "min" : 2]
var d2 = d1
d1["other"] = 7
d2["max"] = 12
print(d1)// ["max": 10, "min": 2, "other": 7]
print(d2)// ["max": 12, "min": 2]
引用類型
class Size {
var width: Int
var height: Int
init(width: Int, height: Int) {
self.width = width
self.height = height
}
}
func test() {
var s1 = Size(width: 10, height: 20)
var s2 = s1
}
引用類型的賦值操作
class Size {
var width: Int
var height: Int
init(width: Int, height: Int) {
self.width = width
self.height = height
}
}
var s1 = Size(width: 10, height: 20)
s1 = Size(width: 11, height: 22)
值類型昏鹃、引用類型的let
struct Point {
var x: Int
var y: Int
}
let p = Point(x: 10, y: 20)
p = Point(x: 11, y: 22)// 報錯
p.x = 33 // 報錯
p.y = 44 // 報錯
class Size {
var width: Int
var height: Int
init(width: Int, height: Int) {
self.width = width
self.height = height
}
}
let s = Size(width: 10, height: 20)
s = Size(width: 11, height: 22) // 報錯
s.width = 33
s.height = 44
嵌套類型
struct Poker {
enum Suit : Character {
case spades = "?", hearts = "?", diamonds = "?", clubs = "?"
}
enum Rank: Int {
case two = 2, three, four, five, six, seven, eight, nine, ten
case jack, queen, king, ace
}
}
print(Poker.Suit.hearts.rawValue)
var suit = Poker.Suit.spades
suit = .diamonds
var rank = Poker.Rank.five
rank = .king
結(jié)構(gòu)體、枚舉诀诊、類都可以進(jìn)行定義方法
// 結(jié)構(gòu)體
struct Point {
var x = 10
var y = 10
func show() {
print("x = \(x), y = \(y)")
}
}
let p = Point()
p.show() // x = 10, y = 10
// 枚舉
enum PokerFace: Character {
case spades = "?", hearts = "?", diamonds = "?", clubs = "?"
func show() {
print("face is \(rawValue)")
}
}
let pf = PokerFace.hearts
pf.show() // face is ?
// 類
class Size {
var width = 10
var height = 10
func show() {
print("width = \(width), height = \(height)")
}
}
let s = Size()
s.show() //width = 10, height = 10
