【问题标题】：Swift equivalent of string literal interfaces? - `request(method: 'post'|'put')` [closed]Swift相当于字符串文字接口？ -`request（方法：'post'|'put'）`[关闭]
【发布时间】：2018-07-30 09:12:07
【问题描述】：

在 TypeScript 中我可以做这样的事情 [docs]:

request(method: 'post'|'put')

但在 Swift 中，我正在编写糟糕的代码，例如：

// See RFC7231 and RFC5789 for more info
enum HttpMethods: String {
    case GET = "GET"
    case HEAD = "HEAD"
    case POST = "POST"
    case PUT = "PUT"
    case DELETE = "DELETE"
    case CONNECT = "CONNECT"
    case OPTIONS = "OPTIONS"
    case TRACE = "TRACE"
    case PATCH = "PATCH"
}

如何在编译时限制 Swift 函数的允许输入？

【问题讨论】：

标签： swift function types swift4 swift-protocols

【解决方案1】：

您的 Swift 大写已关闭。你的意思可能是：

enum HTTPMethod: String {
    case get = "GET"
    case head = "HEAD"
    case post = "POST"
    case put = "PUT"
    case delete = "DELETE"
    case connect = "CONNECT"
    case options = "OPTIONS"
    case trace = "TRACE"
    case patch = "PATCH"
}

如果小写字符串常量没问题，就像你在 Typescript 中所做的那样，你可能会这样写来得到同样的东西。一个字符串枚举自动是它自己的值。

enum HTTPMethods: String {
    case get, head, post, put, delete, connect, options, trace, patch
}

如果你想有小写的常量名，但大写的字符串值，那么你需要使用第一个版本。

要使用它来限制参数，您只需使用类型：

func request(method: HTTPMethod)

【讨论】：

啊是的，就是这样。知道我在正确的轨道附近：P

【解决方案2】：

概述：

使用OptionSet 支持多个值。

代码：

struct HTTPMethod : OptionSet {

    let rawValue : Int

    static let get      = HTTPMethod(rawValue: 1 << 0)
    static let head     = HTTPMethod(rawValue: 1 << 1)
    static let post     = HTTPMethod(rawValue: 1 << 2)
    static let put      = HTTPMethod(rawValue: 1 << 3)
    static let delete   = HTTPMethod(rawValue: 1 << 4)
    static let connect  = HTTPMethod(rawValue: 1 << 5)
    static let trace    = HTTPMethod(rawValue: 1 << 6)
    static let patch    = HTTPMethod(rawValue: 1 << 7)
}

func doSomething(method: HTTPMethod) {


}

doSomething(method: [.get, .head, .put])

参考：

https://developer.apple.com/documentation/swift/optionset

【讨论】：