100

Swift 文档说classes、structs和enums都可以符合协议，我可以达到他们都符合的程度。但是我不能让枚举的行为与类和结构示例非常相似：

protocol ExampleProtocol {
    var simpleDescription: String { get set }
    mutating func adjust()
}

class SimpleClass: ExampleProtocol {
    var simpleDescription: String = "A very simple class."
    var anotherProperty: Int = 69105

    func adjust() {
        simpleDescription += " Now 100% adjusted."
    }
}

var a = SimpleClass()
a.adjust()
let aDescription = a.simpleDescription

struct SimpleStructure: ExampleProtocol {
    var simpleDescription: String = "A simple structure"

    mutating func adjust() {
        simpleDescription += " (adjusted)"
    }
}

var b = SimpleStructure()
b.adjust()
let bDescription = b.simpleDescription

enum SimpleEnum: ExampleProtocol {
    case Base

    var simpleDescription: String {
        get {
            return "A Simple Enum"
        }
        set {
            newValue
        }
    }

    mutating func adjust() {
        self.simpleDescription += ", adjusted"
    }
}

var c = SimpleEnum.Base
c.adjust()
let cDescription = c.simpleDescription

我还没有弄清楚如何通过simpleDescription调用来改变adjust(). 我的示例显然不会这样做，因为getter具有硬编码的值，但是我如何设置simpleDescription同时仍符合的值ExampleProtocol？

4

15 回答 15

166

这是我的尝试：

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}

enum ExampleEnum : ExampleProtocol {
    case Base, Adjusted

    var simpleDescription: String {
        return self.getDescription()
    }

    func getDescription() -> String {
        switch self {
        case .Base:
            return "A simple description of enum"
        case .Adjusted:
            return "Adjusted description of enum"
        }
    }

    mutating func adjust() {
        self = ExampleEnum.Adjusted
    }
}

var c = ExampleEnum.Base
c.adjust()
let cDescription = c.simpleDescription
于 2014-06-04T08:35:22.770 回答
47

这是我的看法。

由于这是 aenum而不是 a class，因此您必须考虑不同（TM）：当您的“状态”发生变化时，您的描述必须发生enum变化（正如@hu-qiang 所指出的那样）。

enum SimpleEnumeration: ExampleProtocol {
  case Basic, Adjusted

  var description: String {
    switch self {
    case .Basic:
      return "A simple Enumeration"
    case .Adjusted:
      return "A simple Enumeration [adjusted]"
    }
  }

  mutating func adjust()  {
    self = .Adjusted
  }
}

var c = SimpleEnumeration.Basic
c.description
c.adjust()
c.description

希望有帮助。

于 2014-06-04T10:52:16.680 回答
11

这是另一种方法，仅使用从旅行中获得的知识，直到那时*

enum SimpleEnumeration: String, ExampleProtocol {
    case Basic = "A simple enumeration", Adjusted = "A simple enumeration (adjusted)"

    var simpleDescription: String {
        get {
            return self.toRaw()
        }
    }

    mutating func adjust() {
        self = .Adjusted
    }
}

var c = SimpleEnumeration.Basic
c.adjust()
let cDescription = c.simpleDescription

如果您想adjust()充当切换开关（尽管没有任何迹象表明这是这种情况），请使用：

mutating func adjust() {
    switch self {
    case .Basic:
        self = .Adjusted
    default:
        self = .Basic
    }
}

*（虽然没有明确提到如何指定返回类型和协议）

于 2014-06-12T16:04:13.513 回答
8

这是一个不改变当前枚举值的解决方案，而是改变它们的实例值（以防它对任何人有用）。

enum ProtoEnumeration : ExampleProtocol {
    case One(String)
    case Two(String)

    var simpleDescription: String {
        get {
            switch self {
            case let .One(desc):
                return desc
            case let .Two(desc):
                return desc
            }
        }
    }
    mutating func adjust() {
        switch self {
        case let .One(desc):
            self = .One(desc + ", adjusted 1")
        case let .Two(desc):
            self = .Two(desc + ", adjusted 2")
        }
    }
}

var p = ProtoEnumeration.One("test")
p.simpleDescription
p.adjust()
p.simpleDescription
于 2014-06-13T23:16:06.547 回答
4

在枚举中定义没有 getter 和 setter 的变量是不可能的，因此不可能有一个可以修改的变量。

您可以遵守协议，但不能像在类中那样具有与变异相同的行为。

于 2014-06-03T11:07:02.933 回答
2

这是一个关于 swift 枚举的链接。

结构和枚举是值类型。默认情况下，值类型的属性不能从其实例方法中修改。关联

然后，您必须使用变异功能。

enum ProtocolEnum: ExampleProtocol {
    case on, off
    var simpleDescription: String {
        switch self {
        case .on:
            return "Switch is ON"
        case .off:
            return "Switch is OFF"
        }
    }
    mutating func adjust() {
        switch self {
        case .on:
            self = off
        case .off:
            self = on
        }
    }
}

var c = ProtocolEnum.on
c.simpleDescription
c.adjust()
let cDescription = c.simpleDescription
于 2014-06-13T03:48:24.157 回答
1

这是基于杰克的回答：

protocol ICanWalk {
    var description: String { get }
    mutating func stepIt()
}

enum TwoStepsForwardThreeStepsBack: Int, ICanWalk {
    case Base = 0, Step1, Step2

    var description: String {
        return "Step \(self.rawValue)"
    }

    mutating func stepIt() {
        if let nextStep = TwoStepsForwardThreeStepsBack( rawValue: self.rawValue + 1 ) {
            // going forward.
            self = nextStep
        } else {
            // back to the base.
            self = TwoStepsForwardThreeStepsBack.Base
        }
    }
}
于 2015-01-15T14:53:10.067 回答
1

另一个选项是让 adjust() 在不同情况之间翻转，如下所示：

enum SimpleEnum: ExampleProtocol {
    case Foo, Bar

    var simpleDescription: String {
    get {
        let value = self == .Foo
            ? "Foo"
            : "Bar"
        return "A simple \(value) enum."
    }
    }

    mutating func adjust() {
        self = self == .Foo
            ? .Bar
            : .Foo
    }
}
于 2014-06-08T12:19:41.083 回答
1

我想出了这个

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}

enum Seat: ExampleProtocol {
    case WindowSeat, MiddleSeat, AisleSeat

    var simpleDescription : String {
        switch self {
        case .WindowSeat:
            return "Window Seat"
        case .MiddleSeat:
            return "Middle Seat"
        case .AisleSeat:
            return "Aisle Seat"
        }
    }

    mutating func adjust() {
        switch self {
        case .WindowSeat:
            self = .MiddleSeat
        case .MiddleSeat:
            self = . AisleSeat
        case .AisleSeat:
            self = .WindowSeat
        }
    }
}

var seat = Seat.MiddleSeat
print(seat.simpleDescription) // Middle Seat
seat.adjust()
print(seat.simpleDescription) // Aisle Seat
于 2016-06-05T19:43:53.227 回答
1

另一种变体：使用关联值来保持和显示上一个选项 （形式为“选择 1，从 2 调整，从 1 调整，从 2 调整，从 1 调整”）

protocol ExampleProtocol {
     var simpleDescription: String { get }
     mutating func adjust()
}

indirect enum EnumWithDescription: ExampleProtocol {
    case option1(EnumWithDescription?)
    case option2(EnumWithDescription?)
    var simpleDescription: String {
        return "Selected " + getDescription()
    }
    internal func getDescription() -> String {
        var currentValue: String
        let previousValue : EnumWithDescription?
        switch self {
        case .option1(let previous):
            currentValue = "1"
            previousValue = previous
        case .option2(let previous):
            currentValue = "2"
            previousValue = previous
        }
        if let adjustedFrom = previousValue?.getDescription() {
            return "\(currentValue) adjusted from \(adjustedFrom)"
        }
        else {
            return "\(currentValue)"
        }
    }
    mutating func adjust() {
        switch self {
        case .option1:
            self = .option2(self)
        case .option2:
            self = .option1(self)
        }
    }
}
var d = EnumWithDescription.option1(nil)
d.simpleDescription
d.adjust()
d.adjust()
d.simpleDescription
// Output: "Selected 1, adjusted from 2, adjusted from 1, adjusted from 2, adjusted from 1"
于 2017-01-17T16:06:53.427 回答
0

这是我的代码

enum SimpleEnum: ExampleProtocol {
    case Base, Adjusted
    var simpleDescription: String {
        get {
            var description = "A simple enum."
            switch self {
            case .Base:
                return description
            case .Adjusted:
                return description + " - [adjusted]"
            }
        }
    }
    mutating func adjust() {
        self = SimpleEnum.Adjusted
    }
}
var simpleEnum = SimpleEnum.Base
simpleEnum.adjust()
simpleEnum.simpleDescription
于 2015-03-11T07:13:55.100 回答
0

我在这里的第一个贡献：

enum SimpleEnum: ExampleProtocol {
    case Basic(String), Adjusted(String)
    init() {
        self = SimpleEnum.Basic("A simple Enum")

    }

    var simpleDescription: String {
        get {
            switch self {
            case let .Basic(string):
                return string
            case let .Adjusted(string):
                return string
            }
        }
    }

    mutating func adjust() {
        self = SimpleEnum.Adjusted("full adjusted")

    }
}

var c = SimpleEnum()
c.adjust()
let cDescription = c.simpleDescription

谢谢别人！

于 2015-06-10T10:41:23.763 回答
0

我当时认为目标只是保留状态并使用描述使当前状态更易于阅读：

enum SimpleEnum: ExampleProtocol {

    case Default, Adjusted

    init() {
        self = .Default
    }

    var simpleDescription: String { get { return "\(self) Value" }}

    mutating func adjust() {
        self = .Adjusted
    }
}

var simpleEnum = SimpleEnum()
simpleEnum.adjust()
let adjustedSimple = simpleEnum.simpleDescript
于 2015-10-23T11:07:42.697 回答
0

这个实验也让我失望了，因为前面的 SimpleClass 和 SimpleStructure 示例显示属性 simpleDescription 在内部被修改，这让我认为我需要做同样的事情。在查看了此处发布的其他答案并阅读了 Apple Swift 2.1 官方文档后，我想出了这个：

protocol ExampleProtocol {
     var simpleDescription: String { get }
     mutating func adjust()
}

enum SimpleEnum: ExampleProtocol {
    case Simple
    case Adjusted

    var simpleDescription: String {
        switch self {
        case .Simple:
            return "A simple enumeration"
        case .Adjusted:
            return "A simple enumeration somewhat changed."
        }
    }

    mutating func adjust() {
        self = .Adjusted
    }

    mutating func restore() {
        self = .Simple
    }
}

var d: SimpleEnum = .Simple
d.simpleDescription

d.adjust()
d.simpleDescription

d.restore()
d.simpleDescription

另请注意，在 Apple 在此实验之前为 SimpleClass 和 SimpleStructure 提供的示例中，简单描述在内部丢失 - 您无法取回原始值（当然，除非您将其保存在类/结构之外）；这就是促使我为 SimpleEnum 示例创建 restore() 方法的原因，它允许您在值之间来回切换它。希望这对某人有用！

于 2015-10-15T19:19:46.060 回答
-1

这个怎么样

enum SimpleEnum : ExampleProtocol {
    case Desc(String)
    init() {
        self = Desc("a simple enum")
    }
    var simpleDescription:String {
        get {
            return (Mirror(reflecting: self).children.first!.value as? String)!
        }
    }
    mutating func adjust() {
        self = SimpleEnum.Desc(self.desc + " adjusted")
    }
}
var e = SimpleEnum()
e.simpleDescription    # => "a simple enum"
e.adjust()
e.simpleDescription    # => "a simple enum adjusted"
于 2015-10-25T10:33:42.360 回答