如何使枚举符合Swift中的协议？ [英] How to make an enum conform to a protocol in Swift?

问题描述

Swift文档说，类，结构和枚举都可以符合协议，我可以得到一个点符合。但是我不能让枚举类似于类和结构示例：

Swift documentation says that classes, structs, and enums can all conform to protocols, and I can get to a point where they all conform. But I can't get the enum to behave quite like the class and struct examples:

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将 simpleDescription 调用 adjust（）的结果。我的示例显然不会这样做，因为 getter 具有硬编码的值，但是如何为 simpleDescription 设置值符合 ExampleProtocol ？

I haven't figured out how to get the simpleDescription to change as a result of calling adjust(). My example obviously won't do that because the getter has a value hard-coded, but how can I set a value for the simpleDescription while still conforming to the ExampleProtocol?

推荐答案

这是我的尝试： p>

This is my attempt:

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

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