Question

有没有办法将枚举关联值类型设置为默认值，而不是为每个情况定义它，如下所示？

enum Device {
    case phone(String)
    case watch(String)
    case tablet(String)
}

我想避免用（String）

重复自己

Answer 1

在这种情况下，可能更容易定义它：

enum DeviceType {
    case phone
    case watch
    case tablet
}

struct Device {
    var type: DeviceType
    var name: String
    ... init, etc.
}

然后你可以彼此独立地处理类型和字符串，因为如果每个枚举的情况都有一个字符串，那么听起来这个字符串可能与枚举值没有直接关系。

Answer 2

如果您对文字感到满意，那么为什么不使用rawValues而不是关联的文字：

enum DeviceType: String {
    case phone = "iPhone X"
    case watch = "Longines"
    case tablet = "Samsung"
    // Only literals can serve as raw values, so next line won't work:
    // case notebook = NSLocalizedString("Any personal computer", comment: "")
}

如果您需要相同类型的可变关联值，则可能会发现字典很有用。

// Add CaseIterable conformance protocol to obtain DeviceType.allCases
enum DeviceType: String, CaseIterable {
    case phone = "iPhone X"
    case watch = "Longines watch"
    case tablet = "Samsung tablet"
    // Only literals can serve as raw values, so next line won't work:
    // case notebook = NSLocalizedString("Any personal computer", comment: "")

    // if you don't want any other vars involved you can add a method to enum
    func localizedName() -> String {
        return NSLocalizedString(self.rawValue, comment: "")
    }
}    
// Create your perfect dict for enum (You'll have to manually add strings to translation)
let deviceTypeLocalized = Dictionary(uniqueKeysWithValues: zip(DeviceType.allCases, DeviceType.allCases.map{ NSLocalizedString($0.rawValue, comment: "") }))
// use (or even change) "associated" values with the power of dicts
let localizedWatchName = deviceTypeLocalized[.watch]
// this is how you get your "associated" value from enum without any external dictionaries, without looking it up.
let localizedTabletName = DeviceType.tablet.localizedName()

具有默认类型

2 个答案: