使用 API 的 background/main 线程出错
Error in background/main thread using API
我尝试调用我的 API,但出现错误:
Modifications to the layout engine must not be performed from a background thread after it has been accessed from the main thread.
我知道我需要调用DispatchQueue
,但我不明白我需要在哪里使用它。
我的代码:
let currentUser = Auth.auth().currentUser
currentUser?.getIDTokenForcingRefresh(true, completion: { (idToken, error) in
if let err = error {
self.unknownError(error: err)
} else {
var request = URLRequest(url: URL(string: "https://phss.ru/api/booking/cancel")!)
request.httpMethod = "POST"
let cancelBooking: [String: Any] = ["booking_id": self.documentIDs]
let jsonData = try! JSONSerialization.data(withJSONObject: cancelBooking, options: [])
request.httpBody = jsonData
request.addValue("Bearer \(idToken!)", forHTTPHeaderField: "Authorization")
let task = URLSession.shared.dataTask(with: request, completionHandler: { (data, response, error) in
if let err = error {
self.unknownError(error: err)
} else {
let alertController = UIAlertController(title: NSLocalizedString("Cancel successful", comment: "Cancel successful"), message: "", preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: NSLocalizableOk, style: .cancel, handler: nil))
self.present(alertController, animated: true, completion: nil)
}
})
task.resume()
}
})
您需要在主线程上显示您的 UIAlertController
,因为 URLSession.shared.dataTask(with:completionHandler:)
的完成回调在后台线程上运行。
DispatchQueue.main.async {
let alertController = UIAlertController(title: NSLocalizedString("Cancel successful", comment: "Cancel successful"), message: "", preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: NSLocalizableOk, style: .cancel, handler: nil))
self.present(alertController, animated: true, completion: nil)
}
我尝试调用我的 API,但出现错误:
Modifications to the layout engine must not be performed from a background thread after it has been accessed from the main thread.
我知道我需要调用DispatchQueue
,但我不明白我需要在哪里使用它。
我的代码:
let currentUser = Auth.auth().currentUser
currentUser?.getIDTokenForcingRefresh(true, completion: { (idToken, error) in
if let err = error {
self.unknownError(error: err)
} else {
var request = URLRequest(url: URL(string: "https://phss.ru/api/booking/cancel")!)
request.httpMethod = "POST"
let cancelBooking: [String: Any] = ["booking_id": self.documentIDs]
let jsonData = try! JSONSerialization.data(withJSONObject: cancelBooking, options: [])
request.httpBody = jsonData
request.addValue("Bearer \(idToken!)", forHTTPHeaderField: "Authorization")
let task = URLSession.shared.dataTask(with: request, completionHandler: { (data, response, error) in
if let err = error {
self.unknownError(error: err)
} else {
let alertController = UIAlertController(title: NSLocalizedString("Cancel successful", comment: "Cancel successful"), message: "", preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: NSLocalizableOk, style: .cancel, handler: nil))
self.present(alertController, animated: true, completion: nil)
}
})
task.resume()
}
})
您需要在主线程上显示您的 UIAlertController
,因为 URLSession.shared.dataTask(with:completionHandler:)
的完成回调在后台线程上运行。
DispatchQueue.main.async {
let alertController = UIAlertController(title: NSLocalizedString("Cancel successful", comment: "Cancel successful"), message: "", preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: NSLocalizableOk, style: .cancel, handler: nil))
self.present(alertController, animated: true, completion: nil)
}