Question

我试图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rawValue对包含空格的字符串不起作用：

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

有任何建议如何获得它？

Answer 1

太复杂，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，所有枚举案例都是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这个问题，添加none个案例并在无法创建枚举的情况下返回它。像这样：

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

Answer 3

你可以define enum这样 -

enum TestEnum: String {
    case Name, Gender, Birth
}

或

enum TestEnum: String { case Name case Gender case Birth }

您可以提供 init 方法，其中默认为其中一个成员值。

enum TestEnum: String { case Name, Gender, Birth init() { self = .Gender } }

在上面的示例中，TestEnum.Name的隐含原始值为＆＃34; Name＆＃34;，依此类推。

使用其rawValue属性访问枚举大小写的原始值：

let testEnum = TestEnum.Name.rawValue // testEnum is "Name" let testEnum1 = TestEnum() // testEnum1 is "Gender"

Answer 4

使用 Swift 4.2 和 CaseIterable 协议，一点都不难！

这里是实现它的示例。

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)
    }
}

您可以轻松地对其进行修改，以基于rawValue返回DataType。希望对您有所帮助！

Answer 5

以下是Swift 4.1中更多可用代码的示例

import UIKit

enum FormData {
  case userName
  case password

  static let array = [userName, password]

  var placeHolder: String {
    switch self {
    case .userName:
      return AppString.name.localized // will return "Name" string
    case .password:
      return AppString.password.localized // will return "Password" string
    }
  }
}

enum AppString: String {
  case name = "Name"
  case password = "Password"

  var localized: String {
    return NSLocalizedString(self.rawValue, comment: "")
  }
}

Answer 6

使用枚举显示原始值

import UIKit

enum car: String {
    case bmw =  "BMW"
    case jaquar = "JAQUAR"
    case rd = "RD"
    case benz = "BENZ"

}


class ViewController: UIViewController {

    @IBOutlet weak var label: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        label.text = car.bmw.rawValue

    }


}

Answer 7

我认为这是Swift 4.2（您可以C＆P到游乐场）的快速，干净的解决方案

import UIKit

public enum SomeEnum: String, CaseIterable {
    case sun,moon,venus,pluto
}

let str = "venus"
let newEnum = SomeEnum.allCases.filter{$0.rawValue == str}.first
// newEnum is optional
if let result = newEnum {
    print(result.rawValue)
}

如何从Swift的原始值中获取枚举？

7 个答案: