设置Alamofire自定义目标文件名称，而不是在Swift 3.0中使用建议的下载destdestination

Question

如何在Swift 3.0中写下以下片段？以下语法在Swift 2

中

    Alamofire.download(.POST, invoice.url,parameters:params, destination: { (url, response) -> NSURL in
        let pathComponent = response.suggestedFilename
        let fileManager = NSFileManager.defaultManager()
        let directoryURL = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
        let fileUrl = directoryURL.URLByAppendingPathComponent(pathComponent)
        return fileUrl
    })
    .progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in
        print(totalBytesRead)
        dispatch_async(dispatch_get_main_queue()) {
            let progress = Double(totalBytesRead) / Double(totalBytesExpectedToRead)
            completionHandler(progress, nil)
        }
    }
    .responseString { response in
        print(response.result.error)
        completionHandler(nil, response.result.error)
    }

Answer 1

在Swift 3中，这是这样的。

let parameters: Parameters = ["foo": "bar"]
let destination: DownloadRequest.DownloadFileDestination = { _, _ in
    let pathComponent = "yourfileName"
    let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    let fileURL = documentsURL.appendPathComponent(pathComponent)
    return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
}
Alamofire.download(urlString, method: .get, parameters: parameters, encoding: JSONEncoding.default, to: destination)
    .downloadProgress(queue: DispatchQueue.global(qos: .utility)) { progress in
        print("Progress: (progress.fractionCompleted)")
    }
    .validate { request, response, temporaryURL, destinationURL in
        // Custom evaluation closure now includes file URLs (allows you to parse out error messages if necessary)
        return .success
    }
    .responseJSON { response in
        debugPrint(response)
        print(response.temporaryURL)
        print(response.destinationURL)
    }

检查Alamofire Documentation或Alamofire 4.0 Migration Guide以获取更多详细信息。

Answer 2

使用func appendingPathComponent(_ pathComponent: String) -> URL代替appendPathComponent。

let destination: DownloadRequest.DownloadFileDestination = { _, _ in
    let pathComponent = "yourfileName"
    let directoryURL: URL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    let folderPath: URL = directoryURL.appendingPathComponent("Downloads", isDirectory: true)
    let fileURL: URL = folderPath.appendingPathComponent(pathComponent)
    return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
}

也可以使用response。

let destination: DownloadRequest.DownloadFileDestination = { _, response in
    let pathComponent = response.suggestedFilename!
    let directoryURL: URL = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask)[0]
    let folderPath: URL = directoryURL.appendingPathComponent("Downloads", isDirectory: true)
    let fileURL: URL = folderPath.appendingPathComponent(pathComponent)
    return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
}