使用XCode-8.2.1，Swift-3.0.2和iOS-10.2.1，
我试图调用两个不同的URLSession.shared.dataTasks（第一个是简单的URL请求，第二个是POST请求）。
由于我的第一个dataTask提供了第二个dataTask的httpBody中所需的结果，因此两个URLSession.shared.dataTasks应该依次运行，一个接一个地运行！ （并且准备代码也应连续运行）。
到目前为止，我尝试使用两个连续的serialQueue.sync{}队列。但是我必须意识到代码无法按照我想要的顺序执行。
日志中的打印语句如下：
Hmmmmmm 2
Hmmmmmm 1
Hmmmmmm 3
（而不是根据需要的1、2、3）！
您如何获得订单1、2、3？
（即，如何确保第二个dataTask的httpBody可以填充来自第一个dataTask的结果？）
这是我的代码：（由于URL已被删除，因此无法执行-但您明白了）！
import UIKit
class ViewController: UIViewController {
let serialQueue = DispatchQueue(label: "myResourceQueue")
var stationID: Int = 0
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.serialQueue.sync {
let myResourceURL = URL(string: "myQueryString1")
let task = URLSession.shared.dataTask(with: myResourceURL!) { (data, response, error) in
if (error != nil) {
// print(error.debugDescription)
} else {
if let myData = data {
do {
let myJson = try JSONSerialization.jsonObject(with: myData, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
// print(myJson)
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
print("Hmmmmmm 1")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
} catch {
// error
}
}
}
}
task.resume()
}
self.serialQueue.sync {
var request = URLRequest(url: URL(string: "myQueryString2")!)
request.httpMethod = "POST"
request.addValue("API_id", forHTTPHeaderField: "Authorization")
request.addValue("application/xml", forHTTPHeaderField: "Content-Type")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
print("Hmmmmmm 2")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
let postString: String = "My_XML_POST_Body"
request.httpBody = postString.data(using: .utf8)
let task = URLSession.shared.dataTask(with: request) { data, response, error in
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
print("Hmmmmmm 3")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
}
task.resume()
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
任何帮助表示赞赏！
最佳答案
我终于找到了解决方案：
受this answer的启发，我介绍了URLSessionDataDelegate以及其委托回调方法（即didReceive response:，didReceive data:和didCompleteWithError error:。
重要提示：您需要为代理设置URLSession，以使引入的URLSessionDelegate的回调方法起作用：使用URLSession（configuration：....），如下所示：
let URLSessionConfig = URLSessionConfiguration.default
let session = URLSession(configuration: URLSessionConfig, delegate: self, delegateQueue: OperationQueue.main)
之后，您就可以开始进行操作了，也就是说，现在的日志是预期的：
Hmmmmmm 1
Hmmmmmm 2
Hmmmmmm 3
这是最终的代码（同样，由于URL被删除，因此也不可执行-但您明白了）！
import UIKit
class ViewController: UIViewController, URLSessionDataDelegate {
var stationID: Int = 0
let URLSessionConfig = URLSessionConfiguration.default
var session: URLSession?
var task1: URLSessionTask?
var task2: URLSessionTask?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.session = URLSession(configuration: URLSessionConfig, delegate: self, delegateQueue: OperationQueue.main)
// prepare dataTask Nr 1
let myResourceURL = URL(string: "myQueryString1")
self.task1 = session?.dataTask(with: myResourceURL!)
// start dataTask Nr 1 (URL-request)
self.task1?.resume()
}
// Optional: Use this method if you want to get a response-size information
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: @escaping (URLSession.ResponseDisposition) -> Void) {
// print(Int(response.expectedContentLength))
completionHandler(URLSession.ResponseDisposition.allow)
}
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
if dataTask == self.task1 {
do {
let myJson = try JSONSerialization.jsonObject(with: myData, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
// print(myJson)
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
print("Hmmmmmm 1")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// prepare dataTask Nr 2
self.task2 = self.session?.dataTask(with: self.prepareMyURLRequest())
} catch {
// error
}
} else if dataTask == self.task2 {
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
print("Hmmmmmm 3")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
} else {
print("unknown dataTask callback")
}
}
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
if (error != nil) {
// print(error.debugDescription)
} else if task == self.task1 {
// start dataTask Nr 2 (POST URL-request)
self.task2?.resume()
}
}
func prepareMyURLRequest() -> URLRequest {
var request = URLRequest(url: URL(string: "myQueryString2")!)
request.httpMethod = "POST"
request.addValue("API_id", forHTTPHeaderField: "Authorization")
request.addValue("application/xml", forHTTPHeaderField: "Content-Type")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
print("Hmmmmmm 2")
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
let postString: String = "My_XML_POST_Body"
request.httpBody = postString.data(using: .utf8)
return request
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}