枚舉的基本用法
enum Direction {
? ? case north
? ? case south
????case east
????case west }
-------------------
enum Direction {
? ? case north, south, east, west
}
----------------------
var dir = Direction.west
dir = Direction.east
dir = .north
print(dir) // north
----------------------
switch dir {
case .north:
? ? print("north")
case .south:
? ? print("south")
case .east:
? ? print("east")
case .west:
? ? print("west")
}
關(guān)聯(lián)值(Associated Values)
有時將枚舉的成員值跟其他類型的值關(guān)聯(lián)存儲在一起，會非常有用
enum Score {
? ? case points(Int)
? ? case grade(Character)
}
var score = Score.points(96)
score = .grade("A")
switch score {
case let .points(i):
? ? print(i, "points")
case let .grade(i):
? ? print("grade", i)
} // grade A
-----------------------
enum Date {
? ? case digit(year: Int, month: Int, day: Int)
? ? case string(String)
}
var date = Date.digit(year: 2011, month: 9, day: 10)
date = .string("2011-09-10")
必要時let也可以改為var
switch date {
case .digit(let year, let month, let day):
? ? print(year, month, day)
case let .string(value):
? ? print(value)
}
關(guān)聯(lián)值舉例
enum Password {
? ? case number(Int, Int, Int, Int)
? ? case gesture(String)
}
var pwd = Password.number(3, 5, 7, 8)
pwd = .gesture("12369")
switch pwd {
case let .number(n1, n2, n3, n4):
? ? print("number is ", n1, n2, n3, n4)
case let .gesture(str):
? ? print("gesture is", str)
}
原始值(Raw Values)
枚舉成員可以使用相同類型的默認(rèn)值預(yù)先對應(yīng)，這個默認(rèn)值叫做:原始值
注意:原始值不占用枚舉變量的內(nèi)存
enum PokerSuit : Character {
????case spade = "?"
????case heart = "?"
????case diamond = "?"
????case club = "?"
}
var suit = PokerSuit.spade?
print(suit) // spade?
print(suit.rawValue) // ??
print(PokerSuit.club.rawValue) // ?
----------------------------
enum Grade : String {
? ? case perfect = "A"
? ? case great = "B"
? ? case good = "C"
? ? case bad = "D"
}
print(Grade.perfect.rawValue) // A
print(Grade.great.rawValue) // B
print(Grade.good.rawValue) // C
print(Grade.bad.rawValue) // D
隱式原始值(Implicitly Assigned Raw Values)
如果枚舉的原始值類型是Int妥色、String垄惧，Swift會自動分配原始值
enum Direction : String {
? ? case north = "north"
? ? case south = "south"
? ? case east = "east"
? ? case west = "west"
}
// 等價于
enum Direction : String {
? ? case north, south, east, west
}
print(Direction.north) // north
print(Direction.north.rawValue) // north
------------------------
enum Season : Int {
? ? case spring, summer, autumn, winter
}
print(Season.spring.rawValue) // 0
print(Season.summer.rawValue) // 1
print(Season.autumn.rawValue) // 2
print(Season.winter.rawValue) // 3
? enum Season : Int {
? ? case spring = 1, summer, autumn = 4, winter
}
print(Season.spring.rawValue) // 1
print(Season.summer.rawValue) // 2
print(Season.autumn.rawValue) // 4
print(Season.winter.rawValue) // 5
遞歸枚舉(Recursive Enumeration)
indirect enum ArithExpr {
????case number(Int)
????case sum(ArithExpr, ArithExpr)
????case difference(ArithExpr, ArithExpr)
}
enum ArithExpr {
????case number(Int)
????indirect case sum(ArithExpr, ArithExpr)
? ? indirect case difference(ArithExpr, ArithExpr)
}
let five = ArithExpr.number(5)
let four = ArithExpr.number(4)
let two = ArithExpr.number(2)
let sum = ArithExpr.sum(five, four)
let difference = ArithExpr.difference(sum, two)
------------------------
func calculate(_ expr: ArithExpr) -> Int {?
switch expr {
? ? case let .number(value):
? ? ? ? return value
????case let .sum(left, right):
????????return calculate(left) + calculate(right)
? ? ?case let .difference(left, right):
????????return calculate(left) - calculate(right)
} }
calculate(difference)
MemoryLayout
可以使用MemoryLayout獲取數(shù)據(jù)類型占用的內(nèi)存大小
enum Password {
? ? case number(Int, Int, Int, Int)
? ? case other
}
MemoryLayout<Password>.stride // 40, 分配占用的空間大小 MemoryLayout<Password>.size // 33, 實際用到的空間大小 MemoryLayout<Password>.alignment // 8, 對齊參數(shù)
var pwd = Password.number(9, 8, 6, 4)
pwd = .other
MemoryLayout.stride(ofValue: pwd) // 40
MemoryLayout.size(ofValue: pwd) // 33
MemoryLayout.alignment(ofValue: pwd) // 8
