在 Swift 中使用 POST 方法接收 JSON 时遇到错误

我正在向后端发送 POST 请求，但是我遇到了这个错误：

The given data was not valid JSON.",
underlyingError: Optional(Error Domain=NSCocoaErrorDomain Code=3840
"JSON text did not start with array or object and option to allow
 fragments not set."
UserInfo={NSDebugDescription=JSON text did not start with array
or object and option to allow fragments not set.})))

这是我用来发送/获取数据的代码：

func fetchDataWithParameters(){

    struct Response: Codable {
        let status: String?
        let error: String?
    }

    let decoder = JSONDecoder()
    HTTP.POST("somelinkhere", parameters: ["date": self.weekDays[self.itemSelectedIndex]]) { response in
        if let error = response.error {
            print("got an error: \(error)")
            return
        }
        do {
            let resp = try decoder.decode(Response.self, from: response.data)
            if let err = resp.error {
                print("got an error: \(err)")
            }
            if let status = resp.status {
                print("completed: \(status)")

            }
        } catch let error {
            print("decode json error: \(error)")
        }
    }
}

我在终端中尝试手动发送 POST 请求，得到了这个结果：

Admins-MacBook-Pro:hello-world admin$ curl -i -H "Accept: application/json" -H "Content-Type: application/json" somelinkhere
HTTP/1.1 200 OK
Server: openresty/1.9.15.1
Date: Thu, 03 May 2018 23:42:04 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 39
Connection: keep-alive
X-Clacks-Overhead: GNU Terry Pratchett

"{\"name\": \"Timo\", \"age\": \"39\"}"

这让我想到唯一可能的错误就是我解码 JSON 的方式不正确。否则为什么会在终端下起作用？有什么想法吗？

如 @patru 建议的一样，我在这里包含了 print：

catch let error {
    print(String(data:response.data, encoding: .utf8)!)
    print("decode json error: \(error)")
}

这是结果：

"{\"name\": \"Mergim\", \"age\": \"39\"}"
decode json error: dataCorrupted(Swift.DecodingError.Context(codingPath: [], debugDescription: "The given data was not valid JSON.", underlyingError: Optional(Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.})))

虽然我使用 curl 得到的是 JSON，但是对于某些原因，Swift 认为这不是有效的 JSON？这是我的后端 post 方法的代码：

@app.route('/', methods=['GET', 'POST'])
def index():

    jsonData = {"name": "Timo", "age": "39"}
    jsonData1 = {"name": "Mergim", "age": "39"}

    if request.method=='GET':
        return json.dumps(jsonData)

    elif request.method=='POST':
        return json.dumps(jsonData1)

编辑

    jsonData = '{"name": "Timo", "age": "39"}'
    jsonData1 = '{"name": "Mergim", "age": "39"}'

更改为：

    jsonData = {"name": "Timo", "age": "39"}
    jsonData1 = {"name": "Mergim", "age": "39"}