Alamofire 4.0 路由器表达式类型不明确，没有更多上下文

Posted 2023-02-24

【中文标题】Alamofire 4.0 路由器表达式类型不明确，没有更多上下文

【英文标题】：Alamofire 4.0 Router Type of expression is ambiguous without more context

【发布时间】：2016-09-22 19:37:54

【问题描述】：

我正在转换为Swift 3.0，并且有一个用于Alamofire 的自定义Router 类。我的代码如下：

enum Router: URLRequestConvertible 

    case get(query: String, params: [String: AnyObject]?)
    case post(query: String, params: [String: AnyObject]?)
    case put(query: String, params: [String: AnyObject]?)
    case delete(query: String, params: [String: AnyObject]?)

    var urlRequest: NSMutableURLRequest 

        // Default to GET
        var httpMethod: HTTPMethod = .get

        let (path, parameters): (String, [String: AnyObject]?) = 
            switch self 
            case .get(let query, let params):
                // Set the request call
                httpMethod = .get
                // Return the query
                return (query, params)
            case .post(let query, let params):
                // Set the request call
                httpMethod = .post
                // Return the query
                return (query, params)
            case .put(let query, let params):
                // Set the request call
                httpMethod = .put
                // Return the query
                return (query, params)
            case .delete(let query, let params):
                // Set the request call
                httpMethod = .delete
                // Return the query
                return (query, params)
            
        ()


        // Create the URL Request
        let urlRequest: NSMutableURLRequest
        if let url =  URL(string: Globals.BASE_URL + path) 
            urlRequest = NSMutableURLRequest(url: url)
         else 
            urlRequest = NSMutableURLRequest()
        

        // set header fields
        if let key = UserDefaults.standard.string(forKey: Globals.NS_KEY_SESSION) 
            urlRequest.setValue(key, forHTTPHeaderField: "X-XX-API")
        

        // Add user agent
        if let userAgent = UserDefaults.standard.string(forKey: Globals.NS_KEY_USER_AGENT) 
            urlRequest.setValue(userAgent, forHTTPHeaderField: "User-Agent")
        

        // Set the HTTP method
        urlRequest.httpMethod = httpMethod.rawValue

        // Set timeout interval to 20 seconds
        urlRequest.timeoutInterval = 20

        return Alamofire.URLEncoding().encode(urlRequest as! URLRequestConvertible, with: parameters)
    

    func asURLRequest() throws -> URLRequest 
    

这给了我一个错误，在 Alamofire.URLEncoding() 处声明 Type of expression is ambiguious without more context。这是什么意思？

在https://github.com/Alamofire/Alamofire/blob/master/Documentation/Alamofire%204.0%20Migration%20Guide.md#parameter-encoding-protocol 的Alamofire 文档中，他们有代码

public protocol ParameterEncoding 
    func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest

【参考方案1】：

这几乎是 How to migrate Alamofire router class to Swift 3? 的副本 检查一下，您将了解如何使用新的ParameterEncoding，尤其是URLRequestConvertible 现在是用func asURLRequest() throws -> URLRequest 实现的，而不是var。

【讨论】：

感谢实现 func 而不是 var 确实有帮助。