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源码
import UIKit
// 指定Int型rawValue
enum Rank : Int {
case Ace = 1
case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten
case Jack, Queen, King
func simpleDescription() -> String {
switch self {
case .Ace:
return "ace"
case .Jack:
return "jack"
case .Queen:
return "queen"
case .King:
return "king"
default:
return String(self.rawValue)
}
}
func compareRank(anotherRank:Rank) -> String {
if self.rawValue > anotherRank.rawValue {
return "\(self.simpleDescription()) is bigger than \(anotherRank.simpleDescription()) !"
} else if self.rawValue < anotherRank.rawValue {
return "\(self.simpleDescription()) is smaller than \(anotherRank.simpleDescription()) !"
} else {
return "\(self.simpleDescription()) is equal to \(anotherRank.simpleDescription()) !"
}
}
}
// 不指定类型是没有rawValue
enum Suit {
case Spades, Hearts, Diamonds, Clubs
func simpleDiscription() -> String {
switch self {
case .Spades:
return "spades"
case .Hearts:
return "hearts"
case .Diamonds:
return "diamonds"
case .Clubs:
return "clubs"
}
}
func color() -> String {
switch self {
case .Spades, .Clubs:
return "black"
case .Hearts, .Diamonds:
return "red"
}
}
}
// 指定String型rawValue
enum CompassPoint: String {
case North,
South,
East,
West
}
// 这是一种嵌套写法
enum ArithmeticExpression {
case Number(Int)
indirect case
Addtion(ArithmeticExpression, ArithmeticExpression)
indirect case
Multiplication(ArithmeticExpression, ArithmeticExpression)
}
// 这是另一种嵌套写法
//indirect enum ArithmeticExpression {
//
// case Number(Int)
//
// case Addition(ArithmeticExpression, ArithmeticExpression)
//
// case Multiplication(ArithmeticExpression, ArithmeticExpression)
//}
func evaluate(expression: ArithmeticExpression) -> Int {
switch expression {
case .Number(let value):
return value
case .Addtion(let left, let right):
return evaluate(left) + evaluate(right)
case .Multiplication(let left, let right):
return evaluate(left) * evaluate(right)
}
}
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let ace = Rank.Ace
_ = ace.rawValue
if let convertedRank = Rank(rawValue: 3) {
_ = convertedRank.simpleDescription()
}
print("\(Rank.Five.compareRank(Rank.Jack))")
print("\(Suit.Diamonds.color())")
print("\(CompassPoint.East.rawValue)")
// 枚举嵌套用法
// evaluate (5 + 4) * 2
let five = ArithmeticExpression.Number(5)
let four = ArithmeticExpression.Number(4)
let sum = ArithmeticExpression.Addtion(five, four)
let product = ArithmeticExpression.Multiplication(sum, ArithmeticExpression.Number(2))
print(evaluate(product))
}
}
输出
5 is smaller than jack !
red
East
18
