枚举的基本用法
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")
}
关联值(Associated Values)
有时将枚举的成员值跟其他类型的值关联存储在一起，会非常有用
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")
必要时let也可以改为var
switch date {
case .digit(let year, let month, let day):
print(year, month, day)
case let .string(value):
print(value)
}
关联值举例
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)
枚举成员可以使用相同类型的默认值预先对应，这个默认值叫做:原始值
注意:原始值不占用枚举变量的内存
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
隐式原始值(Implicitly Assigned Raw Values)
如果枚举的原始值类型是Int、String，Swift会自动分配原始值
enum Direction : String {
case north = "north"
case south = "south"
case east = "east"
case west = "west"
}
// 等价于
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
递归枚举(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获取数据类型占用的内存大小
enum Password {
case number(Int, Int, Int, Int)
case other
}
MemoryLayout
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