如何从Swift的原始值中获取枚举？

Question

我正在尝试从原始值获取枚举类型:

enum TestEnum: String {
    case Name
    case Gender
    case Birth

    var rawValue: String {
        switch self {
        case .Name: return "Name"
        case .Gender: return "Gender"
        case .Birth: return "Birth Day"
        }
    }
}

let name = TestEnum(rawValue: "Name")       //Name
let gender = TestEnum(rawValue: "Gender")   //Gender

但似乎这rawValue对带空格的字符串不起作用:

let birth = TestEnum(rawValue: "Birth Day") //nil

任何建议如何获得它？

Answer 1

太复杂了,只需将原始值直接分配给案例

enum TestEnum: String {
  case Name = "Name"
  case Gender = "Gender"
  case Birth = "Birth Day"
}

let name = TestEnum(rawValue: "Name")!       //Name
let gender = TestEnum(rawValue: "Gender")!   //Gender
let birth = TestEnum(rawValue: "Birth Day")! //Birth

如果案例名称与原始值匹配,您甚至可以省略它

enum TestEnum: String {
  case Name, Gender, Birth = "Birth Day"
}

在Swift 3+中,所有enum案例都是 lowercased

Answer 2

完整的工作示例:

enum TestEnum: String {
    case name = "A Name"
    case otherName
    case test = "Test"
}

let first: TestEnum? = TestEnum(rawValue: "A Name")
let second: TestEnum? = TestEnum(rawValue: "OtherName")
let third: TestEnum? = TestEnum(rawValue: "Test")

print("\(first), \(second), \(third)")

所有这些都可行,但在使用原始值初始化时,它将是可选的.如果这是一个问题,你可以为枚举创建一个初始化器或构造函数来尝试处理它,添加一个nonecase并在无法创建枚举的情况下返回它.像这样的东西:

static func create(rawValue:String) -> TestEnum {
        if let testVal = TestEnum(rawValue: rawValue) {
            return testVal
        }
        else{
            return .none
        }
    }

Answer 3

使用Swift 4.2和CaseIterable协议，它一点也不难！

这是一个如何实现它的示例。

import UIKit

private enum DataType: String, CaseIterable {
    case someDataOne = "an_awesome_string_one"
    case someDataTwo = "an_awesome_string_two"
    case someDataThree = "an_awesome_string_three"
    case someDataFour = "an_awesome_string_four"

    func localizedString() -> String {
        // Internal operation
        // I have a String extension which returns its localized version
        return self.rawValue.localized
    }

    static func fromLocalizedString(localizedString: String) -> DataType? {
        for type in DataType.allCases {
            if type.localizedString() == localizedString {
                return type
            }
        }
        return nil
    }

}

// USAGE EXAMPLE
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    if let dataType = DataType.fromLocalizedString(localizedString: self.title) {
        loadUserData(type: dataType)
    }
}

您可以轻松修改它以根据 rawValue 返回 DataType。我希望它有帮助！