Alamofire - 批量API调用在第二次尝试iOS Swift时生成nil

Question

我有一个名为GetCart()

的函数

GetCart()功能是：

 Alamofire.request(.GET, producturl, encoding: .JSON).validate() .responseJSON(completionHandler: {response in
 switch response.result {
        case .Success:
            print("Validation Successful")
        case .Failure(let error):
            print(error)
        }

})

这个GetCart（）函数通过按钮操作方法在循环中传递：

@IBAction func calltwice(sender: UIButton) {

    for all in 1...5{

        GetCart("24485814")
    }

}

首次尝试时会产生：

Validation Successful
Validation Successful
Validation Successful
Validation Successful
Validation Successful

第二次点击结果：

Error Domain=com.alamofire.error Code=-6006 "JSON could not be serialized. Input data was nil or zero length." UserInfo={NSLocalizedFailureReason=JSON could not be serialized. Input data was nil or zero length.}
Error Domain=com.alamofire.error Code=-6006 "JSON could not be serialized. Input data was nil or zero length." UserInfo={NSLocalizedFailureReason=JSON could not be serialized. Input data was nil or zero length.}
Error Domain=com.alamofire.error Code=-6006 "JSON could not be serialized. Input data was nil or zero length." UserInfo={NSLocalizedFailureReason=JSON could not be serialized. Input data was nil or zero length.}
Validation Successful
Validation Successful

无论第二次点击它循环次数（5或50），只有2次总是通过。 aynone会知道为什么会这样吗？