我有一個(gè)協(xié)議RequestType，它具有如下的relatedType模型。public protocol RequestType: class {    associatedtype Model    var path: String { get set }}public extension RequestType {    public func executeRequest(completionHandler: Result<Model, NSError> -> Void) {        request.response(rootKeyPath: rootKeyPath) { [weak self] (response: Response<Model, NSError>) -> Void in            completionHandler(response.result)            guard let weakSelf = self else { return }            if weakSelf.logging { debugPrint(response) }        }    }}現(xiàn)在，我試圖對(duì)所有失敗的請(qǐng)求進(jìn)行排隊(duì)。public class RequestEventuallyQueue {    static let requestEventuallyQueue = RequestEventuallyQueue()    let queue = [RequestType]()}但是我在線上看到錯(cuò)誤，let queue = [RequestType]()因?yàn)镻rotocol RequestType具有Self或associatedType要求，因此只能用作通用約束。