使用 alamofire 的多部分/表单数据

我正在进行 .post API 调用，并且需要使用 multipart/form-data。我知道如何使用 JSON 进行调用，但我不熟悉 multipart/form-data。使用 JSON，这是一个超级简单的调用。只需创建一个类型参数：

var parameters:Parameters = [:]
parameters["username"] = emailTextField.text!
parameters["password"] = passwordTextField.text!

Alamofire.request(url, method: .post, parameters: parameters, encoding: JSONEncoding.default, headers: headers).responseJSON { (response) in
    //Code here 
}

我们如何使用表单数据来编写它。做到这一点最简单的方法是什么？我不需要上传任何文件或任何东西。我要做的就是用上面这样极其简单的项目打电话。使用表单数据执行此操作的最简洁方法是什么？我确信这是一个非常基本的问题，我四处寻找有关堆栈溢出的帮助，但我只看到它用于更高级的文件调用。我只是想知道如何以最简单的方式执行此操作，本质上是 JSON 调用的替代。

文档中的示例：

Alamofire.upload(
    multipartFormData: { multipartFormData in
        multipartFormData.append(unicornImageURL, withName: "unicorn")
        multipartFormData.append(rainbowImageURL, withName: "rainbow")
    },
    to: "https://httpbin.org/post",
    encodingCompletion: { encodingResult in
        switch encodingResult {
        case .success(let upload, _, _):
            upload.responseJSON { response in
                debugPrint(response)
            }
        case .failure(let encodingError):
            print(encodingError)
        }
    }
)

该方法的完整描述（如果您需要设置 headers.Source https://github.com/Alamofire/Alamofire/blob/master/Source/Alamofire.swift#L376):

/// Encodes `multipartFormData` using `encodingMemoryThreshold` with the default `SessionManager` and calls
/// `encodingCompletion` with new `UploadRequest` using the `url`, `method` and `headers`.
///
/// It is important to understand the memory implications of uploading `MultipartFormData`. If the cummulative
/// payload is small, encoding the data in-memory and directly uploading to a server is the by far the most
/// efficient approach. However, if the payload is too large, encoding the data in-memory could cause your app to
/// be terminated. Larger payloads must first be written to disk using input and output streams to keep the memory
/// footprint low, then the data can be uploaded as a stream from the resulting file. Streaming from disk MUST be
/// used for larger payloads such as video content.
///
/// The `encodingMemoryThreshold` parameter allows Alamofire to automatically determine whether to encode in-memory
/// or stream from disk. If the content length of the `MultipartFormData` is below the `encodingMemoryThreshold`,
/// encoding takes place in-memory. If the content length exceeds the threshold, the data is streamed to disk
/// during the encoding process. Then the result is uploaded as data or as a stream depending on which encoding
/// technique was used.
///
/// - parameter multipartFormData:       The closure used to append body parts to the `MultipartFormData`.
/// - parameter encodingMemoryThreshold: The encoding memory threshold in bytes.
///                                      `multipartFormDataEncodingMemoryThreshold` by default.
/// - parameter url:                     The URL.
/// - parameter method:                  The HTTP method. `.post` by default.
/// - parameter headers:                 The HTTP headers. `nil` by default.
/// - parameter encodingCompletion:      The closure called when the `MultipartFormData` encoding is complete.
public func upload(
    multipartFormData: @escaping (MultipartFormData) -> Void,
    usingThreshold encodingMemoryThreshold: UInt64 = SessionManager.multipartFormDataEncodingMemoryThreshold,
    to url: URLConvertible,
    method: HTTPMethod = .post,
    headers: HTTPHeaders? = nil,
    encodingCompletion: ((SessionManager.MultipartFormDataEncodingResult) -> Void)?)