我将postRequest函数发送到Foursquare的API时收到错误400

Question

getRequest完美地完成并获得了代码200响应和json数据。 postRequest函数没有工作并返回错误400.关于什么可能出错的任何想法？也许我的参数没有正确陈述？!!感谢

---

func getRequest(searchString : String) {

    let latitude = 44.3
    let longitude = 37.2

    let latLongUrl = NSURL(string: "https://api.foursquare.com/v2/venues/search?ll=\(latitude),\(longitude)&client_id=\(kFoursquareAppID)&client_secret=\(kFoursquareAppSecret)&v=20150111") //* find a way to pass the date format into the date area with the YYYYMMDD specific format

    let searchQueryUrl = NSURL(string: "https://api.foursquare.com/v2/venues/search?client_id=\(kFoursquareAppID)&client_secret=\(kFoursquareAppSecret)&v=20150111&ll=\(latitude),\(longitude)&query=\(searchString)")

    let searchQuery2 = NSURL(string: "https://api.foursquare.com/v2/venues/search?client_id=CLIENT_ID&client_secret=CLIENT_SECRET&v=20130815&ll=40.7,-74&query=sushi")

    //In the HTTP request, you need to pass in your client ID, client secret, a version parameter, and any other parameters that the endpoint requires:

    let task2 = NSURLSession.sharedSession().dataTaskWithURL(latLongUrl!, completionHandler: { (data, response, error) -> Void in

        var stringData = NSString(data: data, encoding: NSUTF8StringEncoding)
        println(stringData)
        println(response)

    })

}

---

func postRequest(searchString : String) {

    let latitude = 44.3
    let longitude = 37.2

    let latLon = "\(latitude), \(longitude)"

    var request = NSMutableURLRequest(URL: NSURL(string: "https://api.foursquare.com/v2/venues/search")!)
    let session = NSURLSession.sharedSession()
    request.HTTPMethod = "POST"

    //Setup the Params Dictionary
    var params = [
        "ll" : latLon,
        "client_id"  : kFoursquareAppID,
        "client_secret" : kFoursquareAppSecret,
        "categoryId" : "4bf58dd8d48988d1e0931735",
        "v" : "20150111"]

    //Setup an Error
    var error: NSError?

    request.HTTPBody = NSJSONSerialization.dataWithJSONObject(params, options: nil, error: &error)
    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    request.addValue("application/json", forHTTPHeaderField: "Accept")

    //Call a completion Handler when this url call is complete
    var task = session.dataTaskWithRequest(request, completionHandler: { (data, respose, err) -> Void in

        var stringData = NSString(data: data, encoding: NSUTF8StringEncoding)

        //Convert the String into a dictionary
        var conversionError: NSError?

        //This is the way we can convert the data into a dictionary into those keyValue Pairs
        var jsonDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableLeaves, error: &conversionError) as NSDictionary

        println(jsonDictionary) //this will print out the value we are getting as a dictionary in the console.

    })

    task.resume()
}

---