Swift 2.0 POST Body null

Question

使用数据包分析器，我得到的是我的HTTP正文为空。有什么理由说我的params没有被发送到POST请求中吗？

let request = NSMutableURLRequest(URL: NSURL(string:"SERVERURL")!)
    request.HTTPMethod = "POST"

    do {
        let params = ["returnInt":"5"] as Dictionary<String,String>
        request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: NSJSONWritingOptions.PrettyPrinted)
        request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        request.addValue("application/json", forHTTPHeaderField: "Accept")
    } catch {
        //Do nothing
    }
        let task = NSURLSession.sharedSession().dataTaskWithRequest(request){
        data, response, error in

        if error != nil{
            print("error=\(error)")
            return
        }
        let responseString = NSString(data: data!, encoding: NSUTF8StringEncoding)
        print("\(responseString)")
    }
    task!.resume()

Answer 1

正如我在Playground中看到的println()一样，request.HTTPBody不是 nil 。此外，我的分析器显示 nil ：