与enum和可选元组关联值的Swift模式匹配

Question

我目前正在使用Alamofire,我使用枚举来描述我在自述文件中建议使用的API.

端点表示如下:

public enum API {
    case GetStops(stopCode:String?)
    case GetPhysicalStops
    case GetLinesColors
    case GetNextDepartures(stopCode:String, departureCode:String?, linesCode:String?, destinationsCode:String?)
}

可选参数是互斥的:

 public var URLRequest: NSMutableURLRequest {

        let result:(path:String, parameters:[String:AnyObject]?) = {
            switch self {
            case .GetStops(let stopCode) where stopCode != nil :
                return ("GetStops.json", ["stopCode" : stopCode!])
            case .GetStops(_):
                return ("GetStops.json", nil)
            case .GetPhysicalStops:
                 return ("GetPhysicalStops.json", nil)
            case .GetLinesColors:
                return ("GetLinesColors",nil)
            case .GetNextDepartures(let stopCode, let departureCode, _, _) where departureCode != nil:
                return ("GetNextDepartures", ["stopCode" : stopCode, "departureCode": departureCode!])
            case .GetNextDepartures(let stopCode, _, let linesCode, _) where linesCode != nil:
                return ("GetNextDepartures", ["stopCode" : stopCode, "linesCode": linesCode!])
            case .GetNextDepartures(let stopCode, _, _, let destinationsCode) where destinationsCode != nil:
                return ("GetNextDepartures", ["stopCode" : stopCode, "destinationsCode": destinationsCode!])
            case .GetNextDepartures(let stopCode,_,_,_):
                return ("GetNextDepartures",["stopCode":stopCode])
            }
            }()

是否有办法来自动解开可选包含(像if let),元组内,并避免明确地解开像在此声明:

case .GetStops(let stopCode) where stopCode != nil :
                    return ("GetStops.json", ["stopCode" : stopCode!])

Answer 1

你可以使用.Some(x)模式(.some(x)在Swift 3中):

case .GetStops(let .Some(stopCode)):
     return ("GetStops.json", ["stopCode" : stopCode])

从Swift 2(Xcode 7)开始,这可以缩短为x?模式:

case .GetStops(let stopCode?):
     return ("GetStops.json", ["stopCode" : stopCode])

测试相关值为非零和展开(类似于可选绑定).