swift - alamofire 获取请求返回空值

Question

我有一个问题。我正在使用 alamofire 请求它的返回值。在 alamofire 中，我将返回的 json 转换为我的自定义类，它的工作很好。但是当我从 alamofire 主体中使用这个转换后的类时，它返回了 nil 值。 我在 alamofire 中放置了断点，在那里我转换了 json 值并附加到我的类(class)，它具有值(value)并将它放到我的类(class)中。但在 body 之外它等于零。为什么？

func getZakazDetail(orderID:Int,tableView:UITableView,spinner:UIActivityIndicatorView){

    if flag{
        let zD=ZakazDetailTableViewController()
        Alamofire.request(.GET, "myUrl")
            .responseJSON { response in
                guard response.result.error == nil else {
                    // got an error in getting the data, need to handle it
                    print("error calling GET on /todos/1")
                    print(response.result.error!)
                    return
                }

                if let value = response.result.value {
                    let product = JSON(value)
                    if product != nil{
                        for (_,subJson):(String, JSON) in product {
                            let p=ZakazDetail(id: subJson["id"].int!, tovar: subJson["tovar"].string!, count: subJson["count"].int!, orderid: subJson["orderid"].int!, cena: subJson["cena"].int!)
                            self.zakazDetail.append(p)
                            zD.detail.append(p)
                        }
                    }
                }
        }
        spinner.stopAnimating()
        UIApplication.sharedApplication().networkActivityIndicatorVisible = false
        tableView.reloadData()

    }
    else{
        let alert = UIAlertView(title: "Ошибка",message: "Нету интернета!",delegate: nil,cancelButtonTitle: "OK")
        alert.show()
    }

}

Answer 1

发生这种情况是因为 alamofire 异步加载数据，并且在您将任何内容附加到 zD.detail.append(p) 之前。 为程序添加一个完成处理程序以等待加载完成。

//here you call authenticateUser with a closure that prints responseObject
API().authenticateUser{ (responseObject, error) in
    println(responseObject)
}

然后:

//authenticateUser receives your closure as a parameter
func authenticateUser(completionHandler: (responseObject: String?, error: NSError?) -> ()) {
    //it passes your closure to makeAuthenticateUserCall
    makeAuthenticateUserCall(completionHandler)
}

//makeAuthenticateUserCall receives your closure
func makeAuthenticateUserCall(completionHandler: (responseObject: String?, 
error: NSError?) -> ()) {
    Alamofire.request(.GET, loginUrlString)
        .authenticate(user: "a", password: "b")
        //here you pass a new closure to the responseString method
        .responseString { request, response, responseString, responseError in
            //in this closure body you call your completionHandler closure with the 
            //parameters passed by responseString and your code gets executed 
            //(that in your case just prints the responseObject)
            completionHandler(responseObject: responseString as String!, error: responseError)
    }
}

有关更多信息，请阅读文档:Swift Closures