我正在调用一个执行 URLSession 的方法，但在它执行任何操作之前，会显示一个 UIAlertController 阻塞 UI，直到获得来自请求的某种响应。逻辑告诉我，在主线程上调用该方法的完成 block 中关闭 UIAlertController 将是最佳选择。我的假设是错误的吗？显然是这样，因为呈现的 UIAlertController 确实会显示，但永远不会关闭。帮忙？
block :
getCostandIV { output in
let cost = output["ask"] as! NSNumber
let IV = output["IV"] as! NSNumber
self.enteredCost = cost.stringValue
self.enteredIV = IV.stringValue
DispatchQueue.main.async {
self.progress.dismiss(animated: true, completion: nil)
self.tableView.reloadSections(IndexSet(integer: 1), with: UITableView.RowAnimation.none)
self.canWeSave()
}
}
功能:
func getCostandIV (completionBlock: @escaping (NSMutableDictionary) -> Void) -> Void {
DispatchQueue.main.async {
self.progress = UIAlertController(title: "Retrieving ask price and volatility...", message: nil, preferredStyle: UIAlertController.Style.alert)
self.present(self.progress, animated: true, completion: nil)
}
guard let url = URL(string: "https://api.tdameritrade.com/v1/marketdata/chains?apikey=test&symbol=\(symbol)&contractType=\(type)&strike=\(selectedStrike)&fromDate=\(selectedExpiry)&toDate=\(selectedExpiry)") else {
return
}
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let dataResponse = data,
error == nil else {
//print(error?.localizedDescription ?? "Response Error")
DispatchQueue.main.async {
self.presentedViewController?.dismiss(animated: true, completion: {
let alert = UIAlertController(title: "There was an error retrieving ask price and volatility.", message: "Please try again later.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default))
self.present(alert, animated: true)
})
}
return }
do{
//here dataResponse received from a network request
let jsonResponse = try JSONSerialization.jsonObject(with:
dataResponse, options: [])
// //print(jsonResponse) //Response result
guard let jsonDict = jsonResponse as? NSDictionary else {
return
}
// //print(jsonDict)
var strikeMap : NSDictionary = [:]
if self.type == "CALL" {
strikeMap = jsonDict["callExpDateMap"] as! NSDictionary
} else {
strikeMap = jsonDict["putExpDateMap"] as! NSDictionary
}
self.strikes.removeAllObjects()
let inner = strikeMap.object(forKey: strikeMap.allKeys.first ?? "<#default value#>") as! NSDictionary
let innerAgain = inner.object(forKey: inner.allKeys.first ?? "<#default value#>") as! NSArray
let dict : NSDictionary = innerAgain[0] as! NSDictionary
let dict2 = ["ask" : dict["ask"] as! NSNumber, "IV" : dict["volatility"] as! NSNumber] as NSMutableDictionary
completionBlock(dict2)
} catch let parsingError {
print("Error", parsingError)
}
}
task.resume()
}
编辑:使用self.presentedViewController?.dismiss(animated: true, completion: nil) 没有解决问题。此外，未调用 self.progress 的 dismiss 函数的完成 block 。
编辑 2:presentedViewController 就在关闭之前，回调中的代码为 nil，即使在关闭之前在警报 Controller 上调用了 present？
最佳答案
使用这个，为了消除你的警报，你应该在异步 block 中添加 dismiss 方法，并为此设置定时器，你应该告诉异步 block 从现在到 5 秒开始异步，然后做一些事情:
alert.addAction(UIAlertAction(title: "ok", style: .default,
handler: nil))
viewController.present(alert, animated: true, completion: nil)
// change to desired number of seconds (in this case 5 seconds)
let when = DispatchTime.now() + 5
DispatchQueue.main.asyncAfter(deadline: when){
// your code with delay
alert.dismiss(animated: true, completion: nil)
}
关于ios - 何时何地在 Swift 中关闭 UIAlertController？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56800413/