默认情况下，Alamofire使用POST正文中的“参数列表”对参数进行编码。尝试将编码更改为JSON。这样，Alamofire可以按您期望的那样将字典序列化为JSON字符串：

let parameters = [
    "foo": [1,2,3],
    "bar": [
        "baz": "qux"
    ]
]

Alamofire.request(.POST, "http://httpbin.org/post", parameters: parameters, encoding: .JSON)
// HTTP body: {"foo": [1, 2, 3], "bar": {"baz": "qux"}}

或使用您的代码：

let string = "duke"
let jsonObject = ["$and":[["name":["$bw":string], "country":"gb"]]]
let json = JSON(jsonObject)
let params = ["filters" : json.rawValue, "limit":"1", "KEY":"my_key"]

Alamofire.request(.POST, "http://httpbin.org/post", parameters: params, encoding: .JSON)
    .responseString(encoding: NSUTF8StringEncoding) { request, response, content, error in
        NSLog("Request: %@ - %@\n%@", request.HTTPMethod!, request.URL!, request.HTTPBody.map { body in NSString(data: body, encoding: NSUTF8StringEncoding) ?? "" } ?? "")
        if let response = response {
            NSLog("Response: %@\n%@", response, content ?? "")
        }
}

获取输出：

Request: POST - http://httpbin.org/post
{"filters":{"$and":[{"name":{"$bw":"duke"},"country":"gb"}]},"limit":"1","KEY":"my_key"}

编辑：GET参数中的URL编码的JSON

如果要在GET参数中发送URL编码的JSON，则必须首先生成JSON字符串，然后将其作为字符串传递到参数字典中：

SWIFT 1

let string = "duke"
let jsonObject = ["$and":[["name":["$bw":string], "country":"gb"]]]
let json = JSON(jsonObject)

// Generate the string representation of the JSON value
let jsonString = json.rawString(encoding: NSUTF8StringEncoding, options: nil)!
let params = ["filters" : jsonString, "limit": "1", "KEY": "my_key"]


Alamofire.request(.GET, "http://httpbin.org/post", parameters: params)
    .responseString(encoding: NSUTF8StringEncoding) { request, response, content, error in
        NSLog("Request: %@ - %@\n%@", request.HTTPMethod!, request.URL!, request.HTTPBody.map { body in NSString(data: body, encoding: NSUTF8StringEncoding) ?? "" } ?? "")
        if let response = response {
            NSLog("Response: %@\n%@", response, content ?? "")
        }
}

SWIFT 2

let string = "duke"
let jsonObject = ["$and":[["name":["$bw":string], "country":"gb"]]]
let json = JSON(jsonObject)

// Generate the string representation of the JSON value
let jsonString = json.rawString(NSUTF8StringEncoding)!
let params = ["filters" : jsonString, "limit": "1", "KEY": "my_key"]

Alamofire.request(.GET, "http://httpbin.org/post", parameters: params)
    .responseString(encoding: NSUTF8StringEncoding) { request, response, result in
        NSLog("Request: %@ - %@\n%@", request!.HTTPMethod!, request!.URL!, request!.HTTPBody.map { body in NSString(data: body, encoding: NSUTF8StringEncoding) ?? "" } ?? "")
        switch result {
        case .Success(let value):
            NSLog("Response with content: %@", value)
        case .Failure(let data, _):
            NSLog("Response with error: %@", data ?? NSData())
        }
}

SWIFT 3和Alamofire 4.0

let string = "duke"
let jsonObject = ["$and":[["name":["$bw":string], "country":"gb"]]]
let json = JSON(jsonObject)

// Generate the string representation of the JSON value
let jsonString = json.rawString(.utf8)!
let params = ["filters" : jsonString, "limit": "1", "KEY": "my_key"]

Alamofire.request("http://httpbin.org/post", method: .get, parameters: params)
    .responseString { response in
        #if DEBUG
            let request = response.request
            NSLog("Request: \(request!.httpMethod!) - \(request!.url!.absoluteString)\n\(request!.httpBody.map { body in String(data: body, encoding: .utf8) ?? "" } ?? "")")
            switch response.result {
            case .success(let value):
                print("Response with content \(value)")
            case .failure(let error):
                print("Response with error: \(error as NSError): \(response.data ?? Data())")
            }
        #endif
}

这将生成具有以下URL的GET请求：

http://httpbin.org/post?KEY=my_key&filters=%7B%22%24and%22%3A%5B%7B%22name%22%3A%7B%22%24bw%22%3A%22duke%22%7D%2C%22country%22%3A%22gb%22%7D%5D%7D&limit=1

URL解码为：

http://httpbin.org/post?KEY=my_key&filters={"$and":[{"name":{"$bw":"duke"},"country":"gb"}]}&limit=1